slru.c File Reference

#include "postgres.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include "access/slru.h"
#include "access/transam.h"
#include "access/xlog.h"
#include "access/xlogutils.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/fd.h"
#include "storage/shmem.h"
#include "utils/guc_hooks.h"

Include dependency graph for slru.c:

Go to the source code of this file.

Data Structures
struct	SlruWriteAllData

Macros
#define	MAX_WRITEALL_BUFFERS   16
#define	SLRU_BANK_BITSHIFT   4
#define	SLRU_BANK_SIZE   (1 << SLRU_BANK_BITSHIFT)
#define	SlotGetBankNumber(slotno)   ((slotno) >> SLRU_BANK_BITSHIFT)
#define	INIT_SLRUFILETAG(a, xx_handler, xx_segno)

Typedefs
typedef struct SlruWriteAllData	SlruWriteAllData
typedef struct SlruWriteAllData *	SlruWriteAll

Enumerations
enum	SlruErrorCause {   SLRU_OPEN_FAILED , SLRU_SEEK_FAILED , SLRU_READ_FAILED , SLRU_WRITE_FAILED ,   SLRU_FSYNC_FAILED , SLRU_CLOSE_FAILED }

Functions
static int	SlruFileName (SlruCtl ctl, char *path, int64 segno)
static void	SimpleLruZeroLSNs (SlruCtl ctl, int slotno)
static void	SimpleLruWaitIO (SlruCtl ctl, int slotno)
static void	SlruInternalWritePage (SlruCtl ctl, int slotno, SlruWriteAll fdata)
static bool	SlruPhysicalReadPage (SlruCtl ctl, int64 pageno, int slotno)
static bool	SlruPhysicalWritePage (SlruCtl ctl, int64 pageno, int slotno, SlruWriteAll fdata)
static void	SlruReportIOError (SlruCtl ctl, int64 pageno, TransactionId xid)
static int	SlruSelectLRUPage (SlruCtl ctl, int64 pageno)
static bool	SlruScanDirCbDeleteCutoff (SlruCtl ctl, char *filename, int64 segpage, void *data)
static void	SlruInternalDeleteSegment (SlruCtl ctl, int64 segno)
static void	SlruRecentlyUsed (SlruShared shared, int slotno)
Size	SimpleLruShmemSize (int nslots, int nlsns)
int	SimpleLruAutotuneBuffers (int divisor, int max)
void	SimpleLruInit (SlruCtl ctl, const char *name, int nslots, int nlsns, const char *subdir, int buffer_tranche_id, int bank_tranche_id, SyncRequestHandler sync_handler, bool long_segment_names)
bool	check_slru_buffers (const char *name, int *newval)
int	SimpleLruZeroPage (SlruCtl ctl, int64 pageno)
int	SimpleLruReadPage (SlruCtl ctl, int64 pageno, bool write_ok, TransactionId xid)
int	SimpleLruReadPage_ReadOnly (SlruCtl ctl, int64 pageno, TransactionId xid)
void	SimpleLruWritePage (SlruCtl ctl, int slotno)
bool	SimpleLruDoesPhysicalPageExist (SlruCtl ctl, int64 pageno)
void	SimpleLruWriteAll (SlruCtl ctl, bool allow_redirtied)
void	SimpleLruTruncate (SlruCtl ctl, int64 cutoffPage)
void	SlruDeleteSegment (SlruCtl ctl, int64 segno)
static bool	SlruMayDeleteSegment (SlruCtl ctl, int64 segpage, int64 cutoffPage)
bool	SlruScanDirCbReportPresence (SlruCtl ctl, char *filename, int64 segpage, void *data)
bool	SlruScanDirCbDeleteAll (SlruCtl ctl, char *filename, int64 segpage, void *data)
static bool	SlruCorrectSegmentFilenameLength (SlruCtl ctl, size_t len)
bool	SlruScanDirectory (SlruCtl ctl, SlruScanCallback callback, void *data)
int	SlruSyncFileTag (SlruCtl ctl, const FileTag *ftag, char *path)

Variables
static SlruErrorCause	slru_errcause
static int	slru_errno

Macro Definition Documentation

INIT_SLRUFILETAG

#define INIT_SLRUFILETAG	(		a,
			xx_handler,
			xx_segno
	)

Value:

( \
    memset(&(a), 0, sizeof(FileTag)), \
    (a).handler = (xx_handler), \
    (a).segno = (xx_segno) \
)

Definition at line 157 of file slru.c.

MAX_WRITEALL_BUFFERS

#define MAX_WRITEALL_BUFFERS   16

Definition at line 124 of file slru.c.

SlotGetBankNumber

#define SlotGetBankNumber

(

slotno

)

((slotno) >> SLRU_BANK_BITSHIFT)

Definition at line 149 of file slru.c.

SLRU_BANK_BITSHIFT

#define SLRU_BANK_BITSHIFT   4

Definition at line 143 of file slru.c.

SLRU_BANK_SIZE

#define SLRU_BANK_SIZE   (1 << SLRU_BANK_BITSHIFT)

Definition at line 144 of file slru.c.

Typedef Documentation

SlruWriteAll

typedef struct SlruWriteAllData* SlruWriteAll

Definition at line 133 of file slru.c.

SlruWriteAllData

typedef struct SlruWriteAllData SlruWriteAllData

Enumeration Type Documentation

SlruErrorCause

enum SlruErrorCause

Enumerator
SLRU_OPEN_FAILED
SLRU_SEEK_FAILED
SLRU_READ_FAILED
SLRU_WRITE_FAILED
SLRU_FSYNC_FAILED
SLRU_CLOSE_FAILED

Definition at line 165 of file slru.c.

{
    SLRU_OPEN_FAILED,
    SLRU_SEEK_FAILED,
    SLRU_READ_FAILED,
    SLRU_WRITE_FAILED,
    SLRU_FSYNC_FAILED,
    SLRU_CLOSE_FAILED,
} SlruErrorCause;

Function Documentation

check_slru_buffers()

bool check_slru_buffers	(	const char *	name,
		int *	newval
	)

Definition at line 355 of file slru.c.

{
    /* Valid values are multiples of SLRU_BANK_SIZE */
    if (*newval % SLRU_BANK_SIZE == 0)
        return true;
 
    GUC_check_errdetail("\"%s\" must be a multiple of %d", name,
                        SLRU_BANK_SIZE);
    return false;
}

References GUC_check_errdetail, name, newval, and SLRU_BANK_SIZE.

Referenced by check_commit_ts_buffers(), check_multixact_member_buffers(), check_multixact_offset_buffers(), check_notify_buffers(), check_serial_buffers(), check_subtrans_buffers(), and check_transaction_buffers().

SimpleLruAutotuneBuffers()

int SimpleLruAutotuneBuffers	(	int	divisor,
		int	max
	)

Definition at line 232 of file slru.c.

{
    return Min(max - (max % SLRU_BANK_SIZE),
               Max(SLRU_BANK_SIZE,
                   NBuffers / divisor - (NBuffers / divisor) % SLRU_BANK_SIZE));
}

References Max, Min, NBuffers, and SLRU_BANK_SIZE.

Referenced by CLOGShmemBuffers(), CommitTsShmemBuffers(), and SUBTRANSShmemBuffers().

SimpleLruDoesPhysicalPageExist()

bool SimpleLruDoesPhysicalPageExist	(	SlruCtl	ctl,
		int64	pageno
	)

Definition at line 743 of file slru.c.

{
    int64       segno = pageno / SLRU_PAGES_PER_SEGMENT;
    int         rpageno = pageno % SLRU_PAGES_PER_SEGMENT;
    int         offset = rpageno * BLCKSZ;
    char        path[MAXPGPATH];
    int         fd;
    bool        result;
    off_t       endpos;
 
    /* update the stats counter of checked pages */
    pgstat_count_slru_page_exists(ctl->shared->slru_stats_idx);
 
    SlruFileName(ctl, path, segno);
 
    fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
    if (fd < 0)
    {
        /* expected: file doesn't exist */
        if (errno == ENOENT)
            return false;
 
        /* report error normally */
        slru_errcause = SLRU_OPEN_FAILED;
        slru_errno = errno;
        SlruReportIOError(ctl, pageno, 0);
    }
 
    if ((endpos = lseek(fd, 0, SEEK_END)) < 0)
    {
        slru_errcause = SLRU_SEEK_FAILED;
        slru_errno = errno;
        SlruReportIOError(ctl, pageno, 0);
    }
 
    result = endpos >= (off_t) (offset + BLCKSZ);
 
    if (CloseTransientFile(fd) != 0)
    {
        slru_errcause = SLRU_CLOSE_FAILED;
        slru_errno = errno;
        return false;
    }
 
    return result;
}

References CloseTransientFile(), ctl, endpos, fd(), MAXPGPATH, OpenTransientFile(), PG_BINARY, pgstat_count_slru_page_exists(), SlruWriteAllData::segno, SLRU_CLOSE_FAILED, slru_errcause, slru_errno, SLRU_OPEN_FAILED, SLRU_PAGES_PER_SEGMENT, SLRU_SEEK_FAILED, SlruFileName(), and SlruReportIOError().

Referenced by ActivateCommitTs(), find_multixact_start(), MaybeExtendOffsetSlru(), and test_slru_page_exists().

SimpleLruInit()

void SimpleLruInit	(	SlruCtl	ctl,
		const char *	name,
		int	nslots,
		int	nlsns,
		const char *	subdir,
		int	buffer_tranche_id,
		int	bank_tranche_id,
		SyncRequestHandler	sync_handler,
		bool	long_segment_names
	)

Definition at line 252 of file slru.c.

{
    SlruShared  shared;
    bool        found;
    int         nbanks = nslots / SLRU_BANK_SIZE;
 
    Assert(nslots <= SLRU_MAX_ALLOWED_BUFFERS);
 
    shared = (SlruShared) ShmemInitStruct(name,
                                          SimpleLruShmemSize(nslots, nlsns),
                                          &found);
 
    if (!IsUnderPostmaster)
    {
        /* Initialize locks and shared memory area */
        char       *ptr;
        Size        offset;
 
        Assert(!found);
 
        memset(shared, 0, sizeof(SlruSharedData));
 
        shared->num_slots = nslots;
        shared->lsn_groups_per_page = nlsns;
 
        pg_atomic_init_u64(&shared->latest_page_number, 0);
 
        shared->slru_stats_idx = pgstat_get_slru_index(name);
 
        ptr = (char *) shared;
        offset = MAXALIGN(sizeof(SlruSharedData));
        shared->page_buffer = (char **) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(char *));
        shared->page_status = (SlruPageStatus *) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(SlruPageStatus));
        shared->page_dirty = (bool *) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(bool));
        shared->page_number = (int64 *) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(int64));
        shared->page_lru_count = (int *) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(int));
 
        /* Initialize LWLocks */
        shared->buffer_locks = (LWLockPadded *) (ptr + offset);
        offset += MAXALIGN(nslots * sizeof(LWLockPadded));
        shared->bank_locks = (LWLockPadded *) (ptr + offset);
        offset += MAXALIGN(nbanks * sizeof(LWLockPadded));
        shared->bank_cur_lru_count = (int *) (ptr + offset);
        offset += MAXALIGN(nbanks * sizeof(int));
 
        if (nlsns > 0)
        {
            shared->group_lsn = (XLogRecPtr *) (ptr + offset);
            offset += MAXALIGN(nslots * nlsns * sizeof(XLogRecPtr));
        }
 
        ptr += BUFFERALIGN(offset);
        for (int slotno = 0; slotno < nslots; slotno++)
        {
            LWLockInitialize(&shared->buffer_locks[slotno].lock,
                             buffer_tranche_id);
 
            shared->page_buffer[slotno] = ptr;
            shared->page_status[slotno] = SLRU_PAGE_EMPTY;
            shared->page_dirty[slotno] = false;
            shared->page_lru_count[slotno] = 0;
            ptr += BLCKSZ;
        }
 
        /* Initialize the slot banks. */
        for (int bankno = 0; bankno < nbanks; bankno++)
        {
            LWLockInitialize(&shared->bank_locks[bankno].lock, bank_tranche_id);
            shared->bank_cur_lru_count[bankno] = 0;
        }
 
        /* Should fit to estimated shmem size */
        Assert(ptr - (char *) shared <= SimpleLruShmemSize(nslots, nlsns));
    }
    else
    {
        Assert(found);
        Assert(shared->num_slots == nslots);
    }
 
    /*
     * Initialize the unshared control struct, including directory path. We
     * assume caller set PagePrecedes.
     */
    ctl->shared = shared;
    ctl->sync_handler = sync_handler;
    ctl->long_segment_names = long_segment_names;
    ctl->bank_mask = (nslots / SLRU_BANK_SIZE) - 1;
    strlcpy(ctl->Dir, subdir, sizeof(ctl->Dir));
}

References Assert, SlruSharedData::bank_cur_lru_count, SlruSharedData::bank_locks, SlruSharedData::buffer_locks, BUFFERALIGN, ctl, SlruSharedData::group_lsn, IsUnderPostmaster, SlruSharedData::latest_page_number, LWLockPadded::lock, SlruSharedData::lsn_groups_per_page, LWLockInitialize(), MAXALIGN, name, SlruSharedData::num_slots, SlruSharedData::page_buffer, SlruSharedData::page_dirty, SlruSharedData::page_lru_count, SlruSharedData::page_number, SlruSharedData::page_status, pg_atomic_init_u64(), pgstat_get_slru_index(), ShmemInitStruct(), SimpleLruShmemSize(), SLRU_BANK_SIZE, SLRU_MAX_ALLOWED_BUFFERS, SLRU_PAGE_EMPTY, SlruSharedData::slru_stats_idx, and strlcpy().

Referenced by AsyncShmemInit(), CLOGShmemInit(), CommitTsShmemInit(), MultiXactShmemInit(), SerialInit(), SUBTRANSShmemInit(), and test_slru_shmem_startup().

SimpleLruReadPage()

int SimpleLruReadPage	(	SlruCtl	ctl,
		int64	pageno,
		bool	write_ok,
		TransactionId	xid
	)

Definition at line 502 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    LWLock     *banklock = SimpleLruGetBankLock(ctl, pageno);
 
    Assert(LWLockHeldByMeInMode(banklock, LW_EXCLUSIVE));
 
    /* Outer loop handles restart if we must wait for someone else's I/O */
    for (;;)
    {
        int         slotno;
        bool        ok;
 
        /* See if page already is in memory; if not, pick victim slot */
        slotno = SlruSelectLRUPage(ctl, pageno);
 
        /* Did we find the page in memory? */
        if (shared->page_status[slotno] != SLRU_PAGE_EMPTY &&
            shared->page_number[slotno] == pageno)
        {
            /*
             * If page is still being read in, we must wait for I/O.  Likewise
             * if the page is being written and the caller said that's not OK.
             */
            if (shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS ||
                (shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS &&
                 !write_ok))
            {
                SimpleLruWaitIO(ctl, slotno);
                /* Now we must recheck state from the top */
                continue;
            }
            /* Otherwise, it's ready to use */
            SlruRecentlyUsed(shared, slotno);
 
            /* update the stats counter of pages found in the SLRU */
            pgstat_count_slru_page_hit(shared->slru_stats_idx);
 
            return slotno;
        }
 
        /* We found no match; assert we selected a freeable slot */
        Assert(shared->page_status[slotno] == SLRU_PAGE_EMPTY ||
               (shared->page_status[slotno] == SLRU_PAGE_VALID &&
                !shared->page_dirty[slotno]));
 
        /* Mark the slot read-busy */
        shared->page_number[slotno] = pageno;
        shared->page_status[slotno] = SLRU_PAGE_READ_IN_PROGRESS;
        shared->page_dirty[slotno] = false;
 
        /* Acquire per-buffer lock (cannot deadlock, see notes at top) */
        LWLockAcquire(&shared->buffer_locks[slotno].lock, LW_EXCLUSIVE);
 
        /* Release bank lock while doing I/O */
        LWLockRelease(banklock);
 
        /* Do the read */
        ok = SlruPhysicalReadPage(ctl, pageno, slotno);
 
        /* Set the LSNs for this newly read-in page to zero */
        SimpleLruZeroLSNs(ctl, slotno);
 
        /* Re-acquire bank control lock and update page state */
        LWLockAcquire(banklock, LW_EXCLUSIVE);
 
        Assert(shared->page_number[slotno] == pageno &&
               shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS &&
               !shared->page_dirty[slotno]);
 
        shared->page_status[slotno] = ok ? SLRU_PAGE_VALID : SLRU_PAGE_EMPTY;
 
        LWLockRelease(&shared->buffer_locks[slotno].lock);
 
        /* Now it's okay to ereport if we failed */
        if (!ok)
            SlruReportIOError(ctl, pageno, xid);
 
        SlruRecentlyUsed(shared, slotno);
 
        /* update the stats counter of pages not found in SLRU */
        pgstat_count_slru_page_read(shared->slru_stats_idx);
 
        return slotno;
    }
}

References Assert, SlruSharedData::buffer_locks, ctl, LWLockPadded::lock, LW_EXCLUSIVE, LWLockAcquire(), LWLockHeldByMeInMode(), LWLockRelease(), SlruSharedData::page_dirty, SlruSharedData::page_number, SlruSharedData::page_status, pgstat_count_slru_page_hit(), pgstat_count_slru_page_read(), SimpleLruGetBankLock(), SimpleLruWaitIO(), SimpleLruZeroLSNs(), SLRU_PAGE_EMPTY, SLRU_PAGE_READ_IN_PROGRESS, SLRU_PAGE_VALID, SLRU_PAGE_WRITE_IN_PROGRESS, SlruSharedData::slru_stats_idx, SlruPhysicalReadPage(), SlruRecentlyUsed(), SlruReportIOError(), and SlruSelectLRUPage().

Referenced by asyncQueueAddEntries(), GetMultiXactIdMembers(), RecordNewMultiXact(), SerialAdd(), SetXidCommitTsInPage(), SimpleLruReadPage_ReadOnly(), SubTransSetParent(), test_slru_page_read(), TransactionIdSetPageStatusInternal(), TrimCLOG(), and TrimMultiXact().

SimpleLruReadPage_ReadOnly()

int SimpleLruReadPage_ReadOnly	(	SlruCtl	ctl,
		int64	pageno,
		TransactionId	xid
	)

Definition at line 605 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    LWLock     *banklock = SimpleLruGetBankLock(ctl, pageno);
    int         bankno = pageno & ctl->bank_mask;
    int         bankstart = bankno * SLRU_BANK_SIZE;
    int         bankend = bankstart + SLRU_BANK_SIZE;
 
    /* Try to find the page while holding only shared lock */
    LWLockAcquire(banklock, LW_SHARED);
 
    /* See if page is already in a buffer */
    for (int slotno = bankstart; slotno < bankend; slotno++)
    {
        if (shared->page_status[slotno] != SLRU_PAGE_EMPTY &&
            shared->page_number[slotno] == pageno &&
            shared->page_status[slotno] != SLRU_PAGE_READ_IN_PROGRESS)
        {
            /* See comments for SlruRecentlyUsed macro */
            SlruRecentlyUsed(shared, slotno);
 
            /* update the stats counter of pages found in the SLRU */
            pgstat_count_slru_page_hit(shared->slru_stats_idx);
 
            return slotno;
        }
    }
 
    /* No luck, so switch to normal exclusive lock and do regular read */
    LWLockRelease(banklock);
    LWLockAcquire(banklock, LW_EXCLUSIVE);
 
    return SimpleLruReadPage(ctl, pageno, true, xid);
}

References ctl, LW_EXCLUSIVE, LW_SHARED, LWLockAcquire(), LWLockRelease(), SlruSharedData::page_number, SlruSharedData::page_status, pgstat_count_slru_page_hit(), SimpleLruGetBankLock(), SimpleLruReadPage(), SLRU_BANK_SIZE, SLRU_PAGE_EMPTY, SLRU_PAGE_READ_IN_PROGRESS, SlruSharedData::slru_stats_idx, and SlruRecentlyUsed().

Referenced by asyncQueueReadAllNotifications(), find_multixact_start(), SerialGetMinConflictCommitSeqNo(), SubTransGetParent(), test_slru_page_readonly(), TransactionIdGetCommitTsData(), and TransactionIdGetStatus().

SimpleLruShmemSize()

Size SimpleLruShmemSize	(	int	nslots,
		int	nlsns
	)

Definition at line 199 of file slru.c.

{
    int         nbanks = nslots / SLRU_BANK_SIZE;
    Size        sz;
 
    Assert(nslots <= SLRU_MAX_ALLOWED_BUFFERS);
    Assert(nslots % SLRU_BANK_SIZE == 0);
 
    /* we assume nslots isn't so large as to risk overflow */
    sz = MAXALIGN(sizeof(SlruSharedData));
    sz += MAXALIGN(nslots * sizeof(char *));    /* page_buffer[] */
    sz += MAXALIGN(nslots * sizeof(SlruPageStatus));    /* page_status[] */
    sz += MAXALIGN(nslots * sizeof(bool));  /* page_dirty[] */
    sz += MAXALIGN(nslots * sizeof(int64)); /* page_number[] */
    sz += MAXALIGN(nslots * sizeof(int));   /* page_lru_count[] */
    sz += MAXALIGN(nslots * sizeof(LWLockPadded));  /* buffer_locks[] */
    sz += MAXALIGN(nbanks * sizeof(LWLockPadded));  /* bank_locks[] */
    sz += MAXALIGN(nbanks * sizeof(int));   /* bank_cur_lru_count[] */
 
    if (nlsns > 0)
        sz += MAXALIGN(nslots * nlsns * sizeof(XLogRecPtr));    /* group_lsn[] */
 
    return BUFFERALIGN(sz) + BLCKSZ * nslots;
}

References Assert, BUFFERALIGN, MAXALIGN, SLRU_BANK_SIZE, and SLRU_MAX_ALLOWED_BUFFERS.

Referenced by AsyncShmemSize(), CLOGShmemSize(), CommitTsShmemSize(), MultiXactShmemSize(), PredicateLockShmemSize(), SimpleLruInit(), SUBTRANSShmemSize(), and test_slru_shmem_request().

SimpleLruTruncate()

void SimpleLruTruncate	(	SlruCtl	ctl,
		int64	cutoffPage
	)

Definition at line 1405 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int         prevbank;
 
    /* update the stats counter of truncates */
    pgstat_count_slru_truncate(shared->slru_stats_idx);
 
    /*
     * Scan shared memory and remove any pages preceding the cutoff page, to
     * ensure we won't rewrite them later.  (Since this is normally called in
     * or just after a checkpoint, any dirty pages should have been flushed
     * already ... we're just being extra careful here.)
     */
restart:
 
    /*
     * An important safety check: the current endpoint page must not be
     * eligible for removal.  This check is just a backstop against wraparound
     * bugs elsewhere in SLRU handling, so we don't care if we read a slightly
     * outdated value; therefore we don't add a memory barrier.
     */
    if (ctl->PagePrecedes(pg_atomic_read_u64(&shared->latest_page_number),
                          cutoffPage))
    {
        ereport(LOG,
                (errmsg("could not truncate directory \"%s\": apparent wraparound",
                        ctl->Dir)));
        return;
    }
 
    prevbank = SlotGetBankNumber(0);
    LWLockAcquire(&shared->bank_locks[prevbank].lock, LW_EXCLUSIVE);
    for (int slotno = 0; slotno < shared->num_slots; slotno++)
    {
        int         curbank = SlotGetBankNumber(slotno);
 
        /*
         * If the current bank lock is not same as the previous bank lock then
         * release the previous lock and acquire the new lock.
         */
        if (curbank != prevbank)
        {
            LWLockRelease(&shared->bank_locks[prevbank].lock);
            LWLockAcquire(&shared->bank_locks[curbank].lock, LW_EXCLUSIVE);
            prevbank = curbank;
        }
 
        if (shared->page_status[slotno] == SLRU_PAGE_EMPTY)
            continue;
        if (!ctl->PagePrecedes(shared->page_number[slotno], cutoffPage))
            continue;
 
        /*
         * If page is clean, just change state to EMPTY (expected case).
         */
        if (shared->page_status[slotno] == SLRU_PAGE_VALID &&
            !shared->page_dirty[slotno])
        {
            shared->page_status[slotno] = SLRU_PAGE_EMPTY;
            continue;
        }
 
        /*
         * Hmm, we have (or may have) I/O operations acting on the page, so
         * we've got to wait for them to finish and then start again. This is
         * the same logic as in SlruSelectLRUPage.  (XXX if page is dirty,
         * wouldn't it be OK to just discard it without writing it?
         * SlruMayDeleteSegment() uses a stricter qualification, so we might
         * not delete this page in the end; even if we don't delete it, we
         * won't have cause to read its data again.  For now, keep the logic
         * the same as it was.)
         */
        if (shared->page_status[slotno] == SLRU_PAGE_VALID)
            SlruInternalWritePage(ctl, slotno, NULL);
        else
            SimpleLruWaitIO(ctl, slotno);
 
        LWLockRelease(&shared->bank_locks[prevbank].lock);
        goto restart;
    }
 
    LWLockRelease(&shared->bank_locks[prevbank].lock);
 
    /* Now we can remove the old segment(s) */
    (void) SlruScanDirectory(ctl, SlruScanDirCbDeleteCutoff, &cutoffPage);
}

References SlruSharedData::bank_locks, ctl, ereport, errmsg(), SlruSharedData::latest_page_number, LWLockPadded::lock, LOG, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SlruSharedData::num_slots, SlruSharedData::page_dirty, SlruSharedData::page_number, SlruSharedData::page_status, pg_atomic_read_u64(), pgstat_count_slru_truncate(), SimpleLruWaitIO(), SlotGetBankNumber, SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, SlruSharedData::slru_stats_idx, SlruInternalWritePage(), SlruScanDirCbDeleteCutoff(), and SlruScanDirectory().

Referenced by asyncQueueAdvanceTail(), CheckPointPredicate(), clog_redo(), commit_ts_redo(), PerformOffsetsTruncation(), test_slru_page_truncate(), TruncateCLOG(), TruncateCommitTs(), and TruncateSUBTRANS().

SimpleLruWaitIO()

static void SimpleLruWaitIO ( SlruCtl  ctl, int  slotno  )

static

Definition at line 445 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int         bankno = SlotGetBankNumber(slotno);
 
    Assert(shared->page_status[slotno] != SLRU_PAGE_EMPTY);
 
    /* See notes at top of file */
    LWLockRelease(&shared->bank_locks[bankno].lock);
    LWLockAcquire(&shared->buffer_locks[slotno].lock, LW_SHARED);
    LWLockRelease(&shared->buffer_locks[slotno].lock);
    LWLockAcquire(&shared->bank_locks[bankno].lock, LW_EXCLUSIVE);
 
    /*
     * If the slot is still in an io-in-progress state, then either someone
     * already started a new I/O on the slot, or a previous I/O failed and
     * neglected to reset the page state.  That shouldn't happen, really, but
     * it seems worth a few extra cycles to check and recover from it. We can
     * cheaply test for failure by seeing if the buffer lock is still held (we
     * assume that transaction abort would release the lock).
     */
    if (shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS ||
        shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS)
    {
        if (LWLockConditionalAcquire(&shared->buffer_locks[slotno].lock, LW_SHARED))
        {
            /* indeed, the I/O must have failed */
            if (shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS)
                shared->page_status[slotno] = SLRU_PAGE_EMPTY;
            else                /* write_in_progress */
            {
                shared->page_status[slotno] = SLRU_PAGE_VALID;
                shared->page_dirty[slotno] = true;
            }
            LWLockRelease(&shared->buffer_locks[slotno].lock);
        }
    }
}

References Assert, SlruSharedData::bank_locks, SlruSharedData::buffer_locks, ctl, LWLockPadded::lock, LW_EXCLUSIVE, LW_SHARED, LWLockAcquire(), LWLockConditionalAcquire(), LWLockRelease(), SlruSharedData::page_dirty, SlruSharedData::page_status, SlotGetBankNumber, SLRU_PAGE_EMPTY, SLRU_PAGE_READ_IN_PROGRESS, SLRU_PAGE_VALID, and SLRU_PAGE_WRITE_IN_PROGRESS.

Referenced by SimpleLruReadPage(), SimpleLruTruncate(), SlruDeleteSegment(), SlruInternalWritePage(), and SlruSelectLRUPage().

SimpleLruWriteAll()

void SimpleLruWriteAll	(	SlruCtl	ctl,
		bool	allow_redirtied
	)

Definition at line 1319 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    SlruWriteAllData fdata;
    int64       pageno = 0;
    int         prevbank = SlotGetBankNumber(0);
    bool        ok;
 
    /* update the stats counter of flushes */
    pgstat_count_slru_flush(shared->slru_stats_idx);
 
    /*
     * Find and write dirty pages
     */
    fdata.num_files = 0;
 
    LWLockAcquire(&shared->bank_locks[prevbank].lock, LW_EXCLUSIVE);
 
    for (int slotno = 0; slotno < shared->num_slots; slotno++)
    {
        int         curbank = SlotGetBankNumber(slotno);
 
        /*
         * If the current bank lock is not same as the previous bank lock then
         * release the previous lock and acquire the new lock.
         */
        if (curbank != prevbank)
        {
            LWLockRelease(&shared->bank_locks[prevbank].lock);
            LWLockAcquire(&shared->bank_locks[curbank].lock, LW_EXCLUSIVE);
            prevbank = curbank;
        }
 
        /* Do nothing if slot is unused */
        if (shared->page_status[slotno] == SLRU_PAGE_EMPTY)
            continue;
 
        SlruInternalWritePage(ctl, slotno, &fdata);
 
        /*
         * In some places (e.g. checkpoints), we cannot assert that the slot
         * is clean now, since another process might have re-dirtied it
         * already.  That's okay.
         */
        Assert(allow_redirtied ||
               shared->page_status[slotno] == SLRU_PAGE_EMPTY ||
               (shared->page_status[slotno] == SLRU_PAGE_VALID &&
                !shared->page_dirty[slotno]));
    }
 
    LWLockRelease(&shared->bank_locks[prevbank].lock);
 
    /*
     * Now close any files that were open
     */
    ok = true;
    for (int i = 0; i < fdata.num_files; i++)
    {
        if (CloseTransientFile(fdata.fd[i]) != 0)
        {
            slru_errcause = SLRU_CLOSE_FAILED;
            slru_errno = errno;
            pageno = fdata.segno[i] * SLRU_PAGES_PER_SEGMENT;
            ok = false;
        }
    }
    if (!ok)
        SlruReportIOError(ctl, pageno, InvalidTransactionId);
 
    /* Ensure that directory entries for new files are on disk. */
    if (ctl->sync_handler != SYNC_HANDLER_NONE)
        fsync_fname(ctl->Dir, true);
}

References Assert, SlruSharedData::bank_locks, CloseTransientFile(), ctl, SlruWriteAllData::fd, fsync_fname(), i, InvalidTransactionId, LWLockPadded::lock, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SlruWriteAllData::num_files, SlruSharedData::num_slots, SlruSharedData::page_dirty, SlruSharedData::page_status, pgstat_count_slru_flush(), SlruWriteAllData::segno, SlotGetBankNumber, SLRU_CLOSE_FAILED, slru_errcause, slru_errno, SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, SLRU_PAGES_PER_SEGMENT, SlruSharedData::slru_stats_idx, SlruInternalWritePage(), SlruReportIOError(), and SYNC_HANDLER_NONE.

Referenced by CheckPointCLOG(), CheckPointCommitTs(), CheckPointMultiXact(), CheckPointPredicate(), CheckPointSUBTRANS(), find_multixact_start(), and test_slru_page_writeall().

SimpleLruWritePage()

void SimpleLruWritePage	(	SlruCtl	ctl,
		int	slotno
	)

Definition at line 729 of file slru.c.

{
    Assert(ctl->shared->page_status[slotno] != SLRU_PAGE_EMPTY);
 
    SlruInternalWritePage(ctl, slotno, NULL);
}

References Assert, ctl, SLRU_PAGE_EMPTY, and SlruInternalWritePage().

Referenced by ActivateCommitTs(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), clog_redo(), commit_ts_redo(), MaybeExtendOffsetSlru(), multixact_redo(), and test_slru_page_write().

SimpleLruZeroLSNs()

static void SimpleLruZeroLSNs ( SlruCtl  ctl, int  slotno  )

static

Definition at line 428 of file slru.c.

{
    SlruShared  shared = ctl->shared;
 
    if (shared->lsn_groups_per_page > 0)
        MemSet(&shared->group_lsn[slotno * shared->lsn_groups_per_page], 0,
               shared->lsn_groups_per_page * sizeof(XLogRecPtr));
}

References ctl, SlruSharedData::group_lsn, SlruSharedData::lsn_groups_per_page, and MemSet.

Referenced by SimpleLruReadPage(), and SimpleLruZeroPage().

SimpleLruZeroPage()

int SimpleLruZeroPage	(	SlruCtl	ctl,
		int64	pageno
	)

Definition at line 375 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int         slotno;
 
    Assert(LWLockHeldByMeInMode(SimpleLruGetBankLock(ctl, pageno), LW_EXCLUSIVE));
 
    /* Find a suitable buffer slot for the page */
    slotno = SlruSelectLRUPage(ctl, pageno);
    Assert(shared->page_status[slotno] == SLRU_PAGE_EMPTY ||
           (shared->page_status[slotno] == SLRU_PAGE_VALID &&
            !shared->page_dirty[slotno]) ||
           shared->page_number[slotno] == pageno);
 
    /* Mark the slot as containing this page */
    shared->page_number[slotno] = pageno;
    shared->page_status[slotno] = SLRU_PAGE_VALID;
    shared->page_dirty[slotno] = true;
    SlruRecentlyUsed(shared, slotno);
 
    /* Set the buffer to zeroes */
    MemSet(shared->page_buffer[slotno], 0, BLCKSZ);
 
    /* Set the LSNs for this new page to zero */
    SimpleLruZeroLSNs(ctl, slotno);
 
    /*
     * Assume this page is now the latest active page.
     *
     * Note that because both this routine and SlruSelectLRUPage run with
     * ControlLock held, it is not possible for this to be zeroing a page that
     * SlruSelectLRUPage is going to evict simultaneously.  Therefore, there's
     * no memory barrier here.
     */
    pg_atomic_write_u64(&shared->latest_page_number, pageno);
 
    /* update the stats counter of zeroed pages */
    pgstat_count_slru_page_zeroed(shared->slru_stats_idx);
 
    return slotno;
}

References Assert, ctl, SlruSharedData::latest_page_number, LW_EXCLUSIVE, LWLockHeldByMeInMode(), MemSet, SlruSharedData::page_buffer, SlruSharedData::page_dirty, SlruSharedData::page_number, SlruSharedData::page_status, pg_atomic_write_u64(), pgstat_count_slru_page_zeroed(), SimpleLruGetBankLock(), SimpleLruZeroLSNs(), SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, SlruSharedData::slru_stats_idx, SlruRecentlyUsed(), and SlruSelectLRUPage().

Referenced by asyncQueueAddEntries(), SerialAdd(), test_slru_page_write(), ZeroCLOGPage(), ZeroCommitTsPage(), ZeroMultiXactMemberPage(), ZeroMultiXactOffsetPage(), and ZeroSUBTRANSPage().

SlruCorrectSegmentFilenameLength()

static bool SlruCorrectSegmentFilenameLength ( SlruCtl  ctl, size_t  len  )

inlinestatic

Definition at line 1755 of file slru.c.

{
    if (ctl->long_segment_names)
        return (len == 15);     /* see SlruFileName() */
    else
 
        /*
         * Commit 638cf09e76d allowed 5-character lengths. Later commit
         * 73c986adde5 allowed 6-character length.
         *
         * Note: There is an ongoing plan to migrate all SLRUs to 64-bit page
         * numbers, and the corresponding 15-character file names, which may
         * eventually deprecate the support for 4, 5, and 6-character names.
         */
        return (len == 4 || len == 5 || len == 6);
}

References ctl, and len.

Referenced by SlruScanDirectory().

SlruDeleteSegment()

void SlruDeleteSegment	(	SlruCtl	ctl,
		int64	segno
	)

Definition at line 1523 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int         prevbank = SlotGetBankNumber(0);
    bool        did_write;
 
    /* Clean out any possibly existing references to the segment. */
    LWLockAcquire(&shared->bank_locks[prevbank].lock, LW_EXCLUSIVE);
restart:
    did_write = false;
    for (int slotno = 0; slotno < shared->num_slots; slotno++)
    {
        int         pagesegno;
        int         curbank = SlotGetBankNumber(slotno);
 
        /*
         * If the current bank lock is not same as the previous bank lock then
         * release the previous lock and acquire the new lock.
         */
        if (curbank != prevbank)
        {
            LWLockRelease(&shared->bank_locks[prevbank].lock);
            LWLockAcquire(&shared->bank_locks[curbank].lock, LW_EXCLUSIVE);
            prevbank = curbank;
        }
 
        if (shared->page_status[slotno] == SLRU_PAGE_EMPTY)
            continue;
 
        pagesegno = shared->page_number[slotno] / SLRU_PAGES_PER_SEGMENT;
        /* not the segment we're looking for */
        if (pagesegno != segno)
            continue;
 
        /* If page is clean, just change state to EMPTY (expected case). */
        if (shared->page_status[slotno] == SLRU_PAGE_VALID &&
            !shared->page_dirty[slotno])
        {
            shared->page_status[slotno] = SLRU_PAGE_EMPTY;
            continue;
        }
 
        /* Same logic as SimpleLruTruncate() */
        if (shared->page_status[slotno] == SLRU_PAGE_VALID)
            SlruInternalWritePage(ctl, slotno, NULL);
        else
            SimpleLruWaitIO(ctl, slotno);
 
        did_write = true;
    }
 
    /*
     * Be extra careful and re-check. The IO functions release the control
     * lock, so new pages could have been read in.
     */
    if (did_write)
        goto restart;
 
    SlruInternalDeleteSegment(ctl, segno);
 
    LWLockRelease(&shared->bank_locks[prevbank].lock);
}

References SlruSharedData::bank_locks, ctl, LWLockPadded::lock, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), SlruSharedData::num_slots, SlruSharedData::page_dirty, SlruSharedData::page_number, SlruSharedData::page_status, SlruWriteAllData::segno, SimpleLruWaitIO(), SlotGetBankNumber, SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, SLRU_PAGES_PER_SEGMENT, SlruInternalDeleteSegment(), and SlruInternalWritePage().

Referenced by PerformMembersTruncation(), and test_slru_page_delete().

SlruFileName()

static int SlruFileName ( SlruCtl  ctl, char *  path, int64  segno  )

inlinestatic

Definition at line 91 of file slru.c.

{
    if (ctl->long_segment_names)
    {
        /*
         * We could use 16 characters here but the disadvantage would be that
         * the SLRU segments will be hard to distinguish from WAL segments.
         *
         * For this reason we use 15 characters. It is enough but also means
         * that in the future we can't decrease SLRU_PAGES_PER_SEGMENT easily.
         */
        Assert(segno >= 0 && segno <= INT64CONST(0xFFFFFFFFFFFFFFF));
        return snprintf(path, MAXPGPATH, "%s/%015llX", ctl->Dir,
                        (long long) segno);
    }
    else
    {
        /*
         * Despite the fact that %04X format string is used up to 24 bit
         * integers are allowed. See SlruCorrectSegmentFilenameLength()
         */
        Assert(segno >= 0 && segno <= INT64CONST(0xFFFFFF));
        return snprintf(path, MAXPGPATH, "%s/%04X", (ctl)->Dir,
                        (unsigned int) segno);
    }
}

References Assert, ctl, MAXPGPATH, and snprintf.

Referenced by SimpleLruDoesPhysicalPageExist(), SlruInternalDeleteSegment(), SlruPhysicalReadPage(), SlruPhysicalWritePage(), SlruReportIOError(), and SlruSyncFileTag().

SlruInternalDeleteSegment()

static void SlruInternalDeleteSegment ( SlruCtl  ctl, int64  segno  )

static

Definition at line 1500 of file slru.c.

{
    char        path[MAXPGPATH];
 
    /* Forget any fsync requests queued for this segment. */
    if (ctl->sync_handler != SYNC_HANDLER_NONE)
    {
        FileTag     tag;
 
        INIT_SLRUFILETAG(tag, ctl->sync_handler, segno);
        RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true);
    }
 
    /* Unlink the file. */
    SlruFileName(ctl, path, segno);
    ereport(DEBUG2, (errmsg_internal("removing file \"%s\"", path)));
    unlink(path);
}

References ctl, DEBUG2, ereport, errmsg_internal(), INIT_SLRUFILETAG, MAXPGPATH, RegisterSyncRequest(), SlruWriteAllData::segno, SlruFileName(), SYNC_FORGET_REQUEST, and SYNC_HANDLER_NONE.

Referenced by SlruDeleteSegment(), SlruScanDirCbDeleteAll(), and SlruScanDirCbDeleteCutoff().

SlruInternalWritePage()

static void SlruInternalWritePage ( SlruCtl  ctl, int  slotno, SlruWriteAll  fdata  )

static

Definition at line 652 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int64       pageno = shared->page_number[slotno];
    int         bankno = SlotGetBankNumber(slotno);
    bool        ok;
 
    Assert(shared->page_status[slotno] != SLRU_PAGE_EMPTY);
    Assert(LWLockHeldByMeInMode(SimpleLruGetBankLock(ctl, pageno), LW_EXCLUSIVE));
 
    /* If a write is in progress, wait for it to finish */
    while (shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS &&
           shared->page_number[slotno] == pageno)
    {
        SimpleLruWaitIO(ctl, slotno);
    }
 
    /*
     * Do nothing if page is not dirty, or if buffer no longer contains the
     * same page we were called for.
     */
    if (!shared->page_dirty[slotno] ||
        shared->page_status[slotno] != SLRU_PAGE_VALID ||
        shared->page_number[slotno] != pageno)
        return;
 
    /*
     * Mark the slot write-busy, and clear the dirtybit.  After this point, a
     * transaction status update on this page will mark it dirty again.
     */
    shared->page_status[slotno] = SLRU_PAGE_WRITE_IN_PROGRESS;
    shared->page_dirty[slotno] = false;
 
    /* Acquire per-buffer lock (cannot deadlock, see notes at top) */
    LWLockAcquire(&shared->buffer_locks[slotno].lock, LW_EXCLUSIVE);
 
    /* Release bank lock while doing I/O */
    LWLockRelease(&shared->bank_locks[bankno].lock);
 
    /* Do the write */
    ok = SlruPhysicalWritePage(ctl, pageno, slotno, fdata);
 
    /* If we failed, and we're in a flush, better close the files */
    if (!ok && fdata)
    {
        for (int i = 0; i < fdata->num_files; i++)
            CloseTransientFile(fdata->fd[i]);
    }
 
    /* Re-acquire bank lock and update page state */
    LWLockAcquire(&shared->bank_locks[bankno].lock, LW_EXCLUSIVE);
 
    Assert(shared->page_number[slotno] == pageno &&
           shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS);
 
    /* If we failed to write, mark the page dirty again */
    if (!ok)
        shared->page_dirty[slotno] = true;
 
    shared->page_status[slotno] = SLRU_PAGE_VALID;
 
    LWLockRelease(&shared->buffer_locks[slotno].lock);
 
    /* Now it's okay to ereport if we failed */
    if (!ok)
        SlruReportIOError(ctl, pageno, InvalidTransactionId);
 
    /* If part of a checkpoint, count this as a buffer written. */
    if (fdata)
        CheckpointStats.ckpt_bufs_written++;
}

References Assert, SlruSharedData::bank_locks, SlruSharedData::buffer_locks, CheckpointStats, CheckpointStatsData::ckpt_bufs_written, CloseTransientFile(), ctl, SlruWriteAllData::fd, i, InvalidTransactionId, LWLockPadded::lock, LW_EXCLUSIVE, LWLockAcquire(), LWLockHeldByMeInMode(), LWLockRelease(), SlruWriteAllData::num_files, SlruSharedData::page_dirty, SlruSharedData::page_number, SlruSharedData::page_status, SimpleLruGetBankLock(), SimpleLruWaitIO(), SlotGetBankNumber, SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, SLRU_PAGE_WRITE_IN_PROGRESS, SlruPhysicalWritePage(), and SlruReportIOError().

Referenced by SimpleLruTruncate(), SimpleLruWriteAll(), SimpleLruWritePage(), SlruDeleteSegment(), and SlruSelectLRUPage().

SlruMayDeleteSegment()

static bool SlruMayDeleteSegment ( SlruCtl  ctl, int64  segpage, int64  cutoffPage  )

static

Definition at line 1600 of file slru.c.

{
    int64       seg_last_page = segpage + SLRU_PAGES_PER_SEGMENT - 1;
 
    Assert(segpage % SLRU_PAGES_PER_SEGMENT == 0);
 
    return (ctl->PagePrecedes(segpage, cutoffPage) &&
            ctl->PagePrecedes(seg_last_page, cutoffPage));
}

References Assert, ctl, and SLRU_PAGES_PER_SEGMENT.

Referenced by SlruScanDirCbDeleteCutoff(), and SlruScanDirCbReportPresence().

SlruPhysicalReadPage()

static bool SlruPhysicalReadPage ( SlruCtl  ctl, int64  pageno, int  slotno  )

static

Definition at line 801 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int64       segno = pageno / SLRU_PAGES_PER_SEGMENT;
    int         rpageno = pageno % SLRU_PAGES_PER_SEGMENT;
    off_t       offset = rpageno * BLCKSZ;
    char        path[MAXPGPATH];
    int         fd;
 
    SlruFileName(ctl, path, segno);
 
    /*
     * In a crash-and-restart situation, it's possible for us to receive
     * commands to set the commit status of transactions whose bits are in
     * already-truncated segments of the commit log (see notes in
     * SlruPhysicalWritePage).  Hence, if we are InRecovery, allow the case
     * where the file doesn't exist, and return zeroes instead.
     */
    fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
    if (fd < 0)
    {
        if (errno != ENOENT || !InRecovery)
        {
            slru_errcause = SLRU_OPEN_FAILED;
            slru_errno = errno;
            return false;
        }
 
        ereport(LOG,
                (errmsg("file \"%s\" doesn't exist, reading as zeroes",
                        path)));
        MemSet(shared->page_buffer[slotno], 0, BLCKSZ);
        return true;
    }
 
    errno = 0;
    pgstat_report_wait_start(WAIT_EVENT_SLRU_READ);
    if (pg_pread(fd, shared->page_buffer[slotno], BLCKSZ, offset) != BLCKSZ)
    {
        pgstat_report_wait_end();
        slru_errcause = SLRU_READ_FAILED;
        slru_errno = errno;
        CloseTransientFile(fd);
        return false;
    }
    pgstat_report_wait_end();
 
    if (CloseTransientFile(fd) != 0)
    {
        slru_errcause = SLRU_CLOSE_FAILED;
        slru_errno = errno;
        return false;
    }
 
    return true;
}

References CloseTransientFile(), ctl, ereport, errmsg(), fd(), InRecovery, LOG, MAXPGPATH, MemSet, OpenTransientFile(), SlruSharedData::page_buffer, PG_BINARY, pg_pread, pgstat_report_wait_end(), pgstat_report_wait_start(), SlruWriteAllData::segno, SLRU_CLOSE_FAILED, slru_errcause, slru_errno, SLRU_OPEN_FAILED, SLRU_PAGES_PER_SEGMENT, SLRU_READ_FAILED, and SlruFileName().

Referenced by SimpleLruReadPage().

SlruPhysicalWritePage()

static bool SlruPhysicalWritePage ( SlruCtl  ctl, int64  pageno, int  slotno, SlruWriteAll  fdata  )

static

Definition at line 873 of file slru.c.

{
    SlruShared  shared = ctl->shared;
    int64       segno = pageno / SLRU_PAGES_PER_SEGMENT;
    int         rpageno = pageno % SLRU_PAGES_PER_SEGMENT;
    off_t       offset = rpageno * BLCKSZ;
    char        path[MAXPGPATH];
    int         fd = -1;
 
    /* update the stats counter of written pages */
    pgstat_count_slru_page_written(shared->slru_stats_idx);
 
    /*
     * Honor the write-WAL-before-data rule, if appropriate, so that we do not
     * write out data before associated WAL records.  This is the same action
     * performed during FlushBuffer() in the main buffer manager.
     */
    if (shared->group_lsn != NULL)
    {
        /*
         * We must determine the largest async-commit LSN for the page. This
         * is a bit tedious, but since this entire function is a slow path
         * anyway, it seems better to do this here than to maintain a per-page
         * LSN variable (which'd need an extra comparison in the
         * transaction-commit path).
         */
        XLogRecPtr  max_lsn;
        int         lsnindex;
 
        lsnindex = slotno * shared->lsn_groups_per_page;
        max_lsn = shared->group_lsn[lsnindex++];
        for (int lsnoff = 1; lsnoff < shared->lsn_groups_per_page; lsnoff++)
        {
            XLogRecPtr  this_lsn = shared->group_lsn[lsnindex++];
 
            if (max_lsn < this_lsn)
                max_lsn = this_lsn;
        }
 
        if (!XLogRecPtrIsInvalid(max_lsn))
        {
            /*
             * As noted above, elog(ERROR) is not acceptable here, so if
             * XLogFlush were to fail, we must PANIC.  This isn't much of a
             * restriction because XLogFlush is just about all critical
             * section anyway, but let's make sure.
             */
            START_CRIT_SECTION();
            XLogFlush(max_lsn);
            END_CRIT_SECTION();
        }
    }
 
    /*
     * During a SimpleLruWriteAll, we may already have the desired file open.
     */
    if (fdata)
    {
        for (int i = 0; i < fdata->num_files; i++)
        {
            if (fdata->segno[i] == segno)
            {
                fd = fdata->fd[i];
                break;
            }
        }
    }
 
    if (fd < 0)
    {
        /*
         * If the file doesn't already exist, we should create it.  It is
         * possible for this to need to happen when writing a page that's not
         * first in its segment; we assume the OS can cope with that. (Note:
         * it might seem that it'd be okay to create files only when
         * SimpleLruZeroPage is called for the first page of a segment.
         * However, if after a crash and restart the REDO logic elects to
         * replay the log from a checkpoint before the latest one, then it's
         * possible that we will get commands to set transaction status of
         * transactions that have already been truncated from the commit log.
         * Easiest way to deal with that is to accept references to
         * nonexistent files here and in SlruPhysicalReadPage.)
         *
         * Note: it is possible for more than one backend to be executing this
         * code simultaneously for different pages of the same file. Hence,
         * don't use O_EXCL or O_TRUNC or anything like that.
         */
        SlruFileName(ctl, path, segno);
        fd = OpenTransientFile(path, O_RDWR | O_CREAT | PG_BINARY);
        if (fd < 0)
        {
            slru_errcause = SLRU_OPEN_FAILED;
            slru_errno = errno;
            return false;
        }
 
        if (fdata)
        {
            if (fdata->num_files < MAX_WRITEALL_BUFFERS)
            {
                fdata->fd[fdata->num_files] = fd;
                fdata->segno[fdata->num_files] = segno;
                fdata->num_files++;
            }
            else
            {
                /*
                 * In the unlikely event that we exceed MAX_WRITEALL_BUFFERS,
                 * fall back to treating it as a standalone write.
                 */
                fdata = NULL;
            }
        }
    }
 
    errno = 0;
    pgstat_report_wait_start(WAIT_EVENT_SLRU_WRITE);
    if (pg_pwrite(fd, shared->page_buffer[slotno], BLCKSZ, offset) != BLCKSZ)
    {
        pgstat_report_wait_end();
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;
        slru_errcause = SLRU_WRITE_FAILED;
        slru_errno = errno;
        if (!fdata)
            CloseTransientFile(fd);
        return false;
    }
    pgstat_report_wait_end();
 
    /* Queue up a sync request for the checkpointer. */
    if (ctl->sync_handler != SYNC_HANDLER_NONE)
    {
        FileTag     tag;
 
        INIT_SLRUFILETAG(tag, ctl->sync_handler, segno);
        if (!RegisterSyncRequest(&tag, SYNC_REQUEST, false))
        {
            /* No space to enqueue sync request.  Do it synchronously. */
            pgstat_report_wait_start(WAIT_EVENT_SLRU_SYNC);
            if (pg_fsync(fd) != 0)
            {
                pgstat_report_wait_end();
                slru_errcause = SLRU_FSYNC_FAILED;
                slru_errno = errno;
                CloseTransientFile(fd);
                return false;
            }
            pgstat_report_wait_end();
        }
    }
 
    /* Close file, unless part of flush request. */
    if (!fdata)
    {
        if (CloseTransientFile(fd) != 0)
        {
            slru_errcause = SLRU_CLOSE_FAILED;
            slru_errno = errno;
            return false;
        }
    }
 
    return true;
}

References CloseTransientFile(), ctl, END_CRIT_SECTION, fd(), SlruWriteAllData::fd, SlruSharedData::group_lsn, i, INIT_SLRUFILETAG, SlruSharedData::lsn_groups_per_page, MAX_WRITEALL_BUFFERS, MAXPGPATH, SlruWriteAllData::num_files, OpenTransientFile(), SlruSharedData::page_buffer, PG_BINARY, pg_fsync(), pg_pwrite, pgstat_count_slru_page_written(), pgstat_report_wait_end(), pgstat_report_wait_start(), RegisterSyncRequest(), SlruWriteAllData::segno, SLRU_CLOSE_FAILED, slru_errcause, slru_errno, SLRU_FSYNC_FAILED, SLRU_OPEN_FAILED, SLRU_PAGES_PER_SEGMENT, SlruSharedData::slru_stats_idx, SLRU_WRITE_FAILED, SlruFileName(), START_CRIT_SECTION, SYNC_HANDLER_NONE, SYNC_REQUEST, XLogFlush(), and XLogRecPtrIsInvalid.

Referenced by SlruInternalWritePage().

SlruRecentlyUsed()

static void SlruRecentlyUsed ( SlruShared  shared, int  slotno  )

inlinestatic

Definition at line 1120 of file slru.c.

{
    int         bankno = SlotGetBankNumber(slotno);
    int         new_lru_count = shared->bank_cur_lru_count[bankno];
 
    Assert(shared->page_status[slotno] != SLRU_PAGE_EMPTY);
 
    /*
     * The reason for the if-test is that there are often many consecutive
     * accesses to the same page (particularly the latest page).  By
     * suppressing useless increments of bank_cur_lru_count, we reduce the
     * probability that old pages' counts will "wrap around" and make them
     * appear recently used.
     *
     * We allow this code to be executed concurrently by multiple processes
     * within SimpleLruReadPage_ReadOnly().  As long as int reads and writes
     * are atomic, this should not cause any completely-bogus values to enter
     * the computation.  However, it is possible for either bank_cur_lru_count
     * or individual page_lru_count entries to be "reset" to lower values than
     * they should have, in case a process is delayed while it executes this
     * function.  With care in SlruSelectLRUPage(), this does little harm, and
     * in any case the absolute worst possible consequence is a nonoptimal
     * choice of page to evict.  The gain from allowing concurrent reads of
     * SLRU pages seems worth it.
     */
    if (new_lru_count != shared->page_lru_count[slotno])
    {
        shared->bank_cur_lru_count[bankno] = ++new_lru_count;
        shared->page_lru_count[slotno] = new_lru_count;
    }
}

References Assert, SlruSharedData::bank_cur_lru_count, SlruSharedData::page_lru_count, SlruSharedData::page_status, SlotGetBankNumber, and SLRU_PAGE_EMPTY.

Referenced by SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), and SimpleLruZeroPage().

SlruReportIOError()

static void SlruReportIOError ( SlruCtl  ctl, int64  pageno, TransactionId  xid  )

static

Definition at line 1045 of file slru.c.

{
    int64       segno = pageno / SLRU_PAGES_PER_SEGMENT;
    int         rpageno = pageno % SLRU_PAGES_PER_SEGMENT;
    int         offset = rpageno * BLCKSZ;
    char        path[MAXPGPATH];
 
    SlruFileName(ctl, path, segno);
    errno = slru_errno;
    switch (slru_errcause)
    {
        case SLRU_OPEN_FAILED:
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not access status of transaction %u", xid),
                     errdetail("Could not open file \"%s\": %m.", path)));
            break;
        case SLRU_SEEK_FAILED:
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not access status of transaction %u", xid),
                     errdetail("Could not seek in file \"%s\" to offset %d: %m.",
                               path, offset)));
            break;
        case SLRU_READ_FAILED:
            if (errno)
                ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not access status of transaction %u", xid),
                         errdetail("Could not read from file \"%s\" at offset %d: %m.",
                                   path, offset)));
            else
                ereport(ERROR,
                        (errmsg("could not access status of transaction %u", xid),
                         errdetail("Could not read from file \"%s\" at offset %d: read too few bytes.", path, offset)));
            break;
        case SLRU_WRITE_FAILED:
            if (errno)
                ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not access status of transaction %u", xid),
                         errdetail("Could not write to file \"%s\" at offset %d: %m.",
                                   path, offset)));
            else
                ereport(ERROR,
                        (errmsg("could not access status of transaction %u", xid),
                         errdetail("Could not write to file \"%s\" at offset %d: wrote too few bytes.",
                                   path, offset)));
            break;
        case SLRU_FSYNC_FAILED:
            ereport(data_sync_elevel(ERROR),
                    (errcode_for_file_access(),
                     errmsg("could not access status of transaction %u", xid),
                     errdetail("Could not fsync file \"%s\": %m.",
                               path)));
            break;
        case SLRU_CLOSE_FAILED:
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not access status of transaction %u", xid),
                     errdetail("Could not close file \"%s\": %m.",
                               path)));
            break;
        default:
            /* can't get here, we trust */
            elog(ERROR, "unrecognized SimpleLru error cause: %d",
                 (int) slru_errcause);
            break;
    }
}

References ctl, data_sync_elevel(), elog, ereport, errcode_for_file_access(), errdetail(), errmsg(), ERROR, MAXPGPATH, SlruWriteAllData::segno, SLRU_CLOSE_FAILED, slru_errcause, slru_errno, SLRU_FSYNC_FAILED, SLRU_OPEN_FAILED, SLRU_PAGES_PER_SEGMENT, SLRU_READ_FAILED, SLRU_SEEK_FAILED, SLRU_WRITE_FAILED, and SlruFileName().

Referenced by SimpleLruDoesPhysicalPageExist(), SimpleLruReadPage(), SimpleLruWriteAll(), and SlruInternalWritePage().

SlruScanDirCbDeleteAll()

bool SlruScanDirCbDeleteAll	(	SlruCtl	ctl,
		char *	filename,
		int64	segpage,
		void *	data
	)

Definition at line 1741 of file slru.c.

{
    SlruInternalDeleteSegment(ctl, segpage / SLRU_PAGES_PER_SEGMENT);
 
    return false;               /* keep going */
}

References ctl, SLRU_PAGES_PER_SEGMENT, and SlruInternalDeleteSegment().

Referenced by AsyncShmemInit(), DeactivateCommitTs(), and test_slru_scan_cb().

SlruScanDirCbDeleteCutoff()

static bool SlruScanDirCbDeleteCutoff ( SlruCtl  ctl, char *  filename, int64  segpage, void *  data  )

static

Definition at line 1725 of file slru.c.

{
    int64       cutoffPage = *(int64 *) data;
 
    if (SlruMayDeleteSegment(ctl, segpage, cutoffPage))
        SlruInternalDeleteSegment(ctl, segpage / SLRU_PAGES_PER_SEGMENT);
 
    return false;               /* keep going */
}

References ctl, data, SLRU_PAGES_PER_SEGMENT, SlruInternalDeleteSegment(), and SlruMayDeleteSegment().

Referenced by SimpleLruTruncate().

SlruScanDirCbReportPresence()

bool SlruScanDirCbReportPresence	(	SlruCtl	ctl,
		char *	filename,
		int64	segpage,
		void *	data
	)

Definition at line 1709 of file slru.c.

{
    int64       cutoffPage = *(int64 *) data;
 
    if (SlruMayDeleteSegment(ctl, segpage, cutoffPage))
        return true;            /* found one; don't iterate any more */
 
    return false;               /* keep going */
}

References ctl, data, and SlruMayDeleteSegment().

Referenced by TruncateCLOG(), and TruncateCommitTs().

SlruScanDirectory()

bool SlruScanDirectory	(	SlruCtl	ctl,
		SlruScanCallback	callback,
		void *	data
	)

Definition at line 1788 of file slru.c.

{
    bool        retval = false;
    DIR        *cldir;
    struct dirent *clde;
    int64       segno;
    int64       segpage;
 
    cldir = AllocateDir(ctl->Dir);
    while ((clde = ReadDir(cldir, ctl->Dir)) != NULL)
    {
        size_t      len;
 
        len = strlen(clde->d_name);
 
        if (SlruCorrectSegmentFilenameLength(ctl, len) &&
            strspn(clde->d_name, "0123456789ABCDEF") == len)
        {
            segno = strtoi64(clde->d_name, NULL, 16);
            segpage = segno * SLRU_PAGES_PER_SEGMENT;
 
            elog(DEBUG2, "SlruScanDirectory invoking callback on %s/%s",
                 ctl->Dir, clde->d_name);
            retval = callback(ctl, clde->d_name, segpage, data);
            if (retval)
                break;
        }
    }
    FreeDir(cldir);
 
    return retval;
}

References AllocateDir(), callback(), ctl, dirent::d_name, data, DEBUG2, elog, FreeDir(), len, ReadDir(), SLRU_PAGES_PER_SEGMENT, SlruCorrectSegmentFilenameLength(), and strtoi64.

Referenced by AsyncShmemInit(), DeactivateCommitTs(), SimpleLruTruncate(), test_slru_delete_all(), TruncateCLOG(), TruncateCommitTs(), and TruncateMultiXact().

SlruSelectLRUPage()

static int SlruSelectLRUPage ( SlruCtl  ctl, int64  pageno  )

static

Definition at line 1166 of file slru.c.

{
    SlruShared  shared = ctl->shared;
 
    /* Outer loop handles restart after I/O */
    for (;;)
    {
        int         cur_count;
        int         bestvalidslot = 0;  /* keep compiler quiet */
        int         best_valid_delta = -1;
        int64       best_valid_page_number = 0; /* keep compiler quiet */
        int         bestinvalidslot = 0;    /* keep compiler quiet */
        int         best_invalid_delta = -1;
        int64       best_invalid_page_number = 0;   /* keep compiler quiet */
        int         bankno = pageno & ctl->bank_mask;
        int         bankstart = bankno * SLRU_BANK_SIZE;
        int         bankend = bankstart + SLRU_BANK_SIZE;
 
        Assert(LWLockHeldByMe(SimpleLruGetBankLock(ctl, pageno)));
 
        /* See if page already has a buffer assigned */
        for (int slotno = 0; slotno < shared->num_slots; slotno++)
        {
            if (shared->page_status[slotno] != SLRU_PAGE_EMPTY &&
                shared->page_number[slotno] == pageno)
                return slotno;
        }
 
        /*
         * If we find any EMPTY slot, just select that one. Else choose a
         * victim page to replace.  We normally take the least recently used
         * valid page, but we will never take the slot containing
         * latest_page_number, even if it appears least recently used.  We
         * will select a slot that is already I/O busy only if there is no
         * other choice: a read-busy slot will not be least recently used once
         * the read finishes, and waiting for an I/O on a write-busy slot is
         * inferior to just picking some other slot.  Testing shows the slot
         * we pick instead will often be clean, allowing us to begin a read at
         * once.
         *
         * Normally the page_lru_count values will all be different and so
         * there will be a well-defined LRU page.  But since we allow
         * concurrent execution of SlruRecentlyUsed() within
         * SimpleLruReadPage_ReadOnly(), it is possible that multiple pages
         * acquire the same lru_count values.  In that case we break ties by
         * choosing the furthest-back page.
         *
         * Notice that this next line forcibly advances cur_lru_count to a
         * value that is certainly beyond any value that will be in the
         * page_lru_count array after the loop finishes.  This ensures that
         * the next execution of SlruRecentlyUsed will mark the page newly
         * used, even if it's for a page that has the current counter value.
         * That gets us back on the path to having good data when there are
         * multiple pages with the same lru_count.
         */
        cur_count = (shared->bank_cur_lru_count[bankno])++;
        for (int slotno = bankstart; slotno < bankend; slotno++)
        {
            int         this_delta;
            int64       this_page_number;
 
            if (shared->page_status[slotno] == SLRU_PAGE_EMPTY)
                return slotno;
 
            this_delta = cur_count - shared->page_lru_count[slotno];
            if (this_delta < 0)
            {
                /*
                 * Clean up in case shared updates have caused cur_count
                 * increments to get "lost".  We back off the page counts,
                 * rather than trying to increase cur_count, to avoid any
                 * question of infinite loops or failure in the presence of
                 * wrapped-around counts.
                 */
                shared->page_lru_count[slotno] = cur_count;
                this_delta = 0;
            }
 
            /*
             * If this page is the one most recently zeroed, don't consider it
             * an eviction candidate. See comments in SimpleLruZeroPage for an
             * explanation about the lack of a memory barrier here.
             */
            this_page_number = shared->page_number[slotno];
            if (this_page_number ==
                pg_atomic_read_u64(&shared->latest_page_number))
                continue;
 
            if (shared->page_status[slotno] == SLRU_PAGE_VALID)
            {
                if (this_delta > best_valid_delta ||
                    (this_delta == best_valid_delta &&
                     ctl->PagePrecedes(this_page_number,
                                       best_valid_page_number)))
                {
                    bestvalidslot = slotno;
                    best_valid_delta = this_delta;
                    best_valid_page_number = this_page_number;
                }
            }
            else
            {
                if (this_delta > best_invalid_delta ||
                    (this_delta == best_invalid_delta &&
                     ctl->PagePrecedes(this_page_number,
                                       best_invalid_page_number)))
                {
                    bestinvalidslot = slotno;
                    best_invalid_delta = this_delta;
                    best_invalid_page_number = this_page_number;
                }
            }
        }
 
        /*
         * If all pages (except possibly the latest one) are I/O busy, we'll
         * have to wait for an I/O to complete and then retry.  In that
         * unhappy case, we choose to wait for the I/O on the least recently
         * used slot, on the assumption that it was likely initiated first of
         * all the I/Os in progress and may therefore finish first.
         */
        if (best_valid_delta < 0)
        {
            SimpleLruWaitIO(ctl, bestinvalidslot);
            continue;
        }
 
        /*
         * If the selected page is clean, we're set.
         */
        if (!shared->page_dirty[bestvalidslot])
            return bestvalidslot;
 
        /*
         * Write the page.
         */
        SlruInternalWritePage(ctl, bestvalidslot, NULL);
 
        /*
         * Now loop back and try again.  This is the easiest way of dealing
         * with corner cases such as the victim page being re-dirtied while we
         * wrote it.
         */
    }
}

References Assert, SlruSharedData::bank_cur_lru_count, ctl, SlruSharedData::latest_page_number, LWLockHeldByMe(), SlruSharedData::num_slots, SlruSharedData::page_dirty, SlruSharedData::page_lru_count, SlruSharedData::page_number, SlruSharedData::page_status, pg_atomic_read_u64(), SimpleLruGetBankLock(), SimpleLruWaitIO(), SLRU_BANK_SIZE, SLRU_PAGE_EMPTY, SLRU_PAGE_VALID, and SlruInternalWritePage().

Referenced by SimpleLruReadPage(), and SimpleLruZeroPage().

SlruSyncFileTag()

int SlruSyncFileTag	(	SlruCtl	ctl,
		const FileTag *	ftag,
		char *	path
	)

Definition at line 1828 of file slru.c.

{
    int         fd;
    int         save_errno;
    int         result;
 
    SlruFileName(ctl, path, ftag->segno);
 
    fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
    if (fd < 0)
        return -1;
 
    pgstat_report_wait_start(WAIT_EVENT_SLRU_FLUSH_SYNC);
    result = pg_fsync(fd);
    pgstat_report_wait_end();
    save_errno = errno;
 
    CloseTransientFile(fd);
 
    errno = save_errno;
    return result;
}

References CloseTransientFile(), ctl, fd(), OpenTransientFile(), PG_BINARY, pg_fsync(), pgstat_report_wait_end(), pgstat_report_wait_start(), FileTag::segno, and SlruFileName().

Referenced by clogsyncfiletag(), committssyncfiletag(), multixactmemberssyncfiletag(), multixactoffsetssyncfiletag(), and test_slru_page_sync().

Variable Documentation

slru_errcause

SlruErrorCause slru_errcause

static

Definition at line 175 of file slru.c.

Referenced by SimpleLruDoesPhysicalPageExist(), SimpleLruWriteAll(), SlruPhysicalReadPage(), SlruPhysicalWritePage(), and SlruReportIOError().

slru_errno

int slru_errno

static

Definition at line 176 of file slru.c.

Referenced by SimpleLruDoesPhysicalPageExist(), SimpleLruWriteAll(), SlruPhysicalReadPage(), SlruPhysicalWritePage(), and SlruReportIOError().