instrument.c

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/*-------------------------------------------------------------------------
 *
 * instrument.c
 *   functions for instrumentation of plan execution
 *
 *
 * Copyright (c) 2001-2021, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/executor/instrument.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <unistd.h>

#include "executor/instrument.h"

BufferUsage pgBufferUsage;
static BufferUsage save_pgBufferUsage;
WalUsage    pgWalUsage;
static WalUsage save_pgWalUsage;

static void BufferUsageAdd(BufferUsage *dst, const BufferUsage *add);
static void WalUsageAdd(WalUsage *dst, WalUsage *add);


/* Allocate new instrumentation structure(s) */
Instrumentation *
InstrAlloc(int n, int instrument_options, bool async_mode)
{
    Instrumentation *instr;

    /* initialize all fields to zeroes, then modify as needed */
    instr = palloc0(n * sizeof(Instrumentation));
    if (instrument_options & (INSTRUMENT_BUFFERS | INSTRUMENT_TIMER | INSTRUMENT_WAL))
    {
        bool        need_buffers = (instrument_options & INSTRUMENT_BUFFERS) != 0;
        bool        need_wal = (instrument_options & INSTRUMENT_WAL) != 0;
        bool        need_timer = (instrument_options & INSTRUMENT_TIMER) != 0;
        int         i;

        for (i = 0; i < n; i++)
        {
            instr[i].need_bufusage = need_buffers;
            instr[i].need_walusage = need_wal;
            instr[i].need_timer = need_timer;
            instr[i].async_mode = async_mode;
        }
    }

    return instr;
}

/* Initialize a pre-allocated instrumentation structure. */
void
InstrInit(Instrumentation *instr, int instrument_options)
{
    memset(instr, 0, sizeof(Instrumentation));
    instr->need_bufusage = (instrument_options & INSTRUMENT_BUFFERS) != 0;
    instr->need_walusage = (instrument_options & INSTRUMENT_WAL) != 0;
    instr->need_timer = (instrument_options & INSTRUMENT_TIMER) != 0;
}

/* Entry to a plan node */
void
InstrStartNode(Instrumentation *instr)
{
    if (instr->need_timer &&
        !INSTR_TIME_SET_CURRENT_LAZY(instr->starttime))
        elog(ERROR, "InstrStartNode called twice in a row");

    /* save buffer usage totals at node entry, if needed */
    if (instr->need_bufusage)
        instr->bufusage_start = pgBufferUsage;

    if (instr->need_walusage)
        instr->walusage_start = pgWalUsage;
}

/* Exit from a plan node */
void
InstrStopNode(Instrumentation *instr, double nTuples)
{
    double      save_tuplecount = instr->tuplecount;
    instr_time  endtime;

    /* count the returned tuples */
    instr->tuplecount += nTuples;

    /* let's update the time only if the timer was requested */
    if (instr->need_timer)
    {
        if (INSTR_TIME_IS_ZERO(instr->starttime))
            elog(ERROR, "InstrStopNode called without start");

        INSTR_TIME_SET_CURRENT(endtime);
        INSTR_TIME_ACCUM_DIFF(instr->counter, endtime, instr->starttime);

        INSTR_TIME_SET_ZERO(instr->starttime);
    }

    /* Add delta of buffer usage since entry to node's totals */
    if (instr->need_bufusage)
        BufferUsageAccumDiff(&instr->bufusage,
                             &pgBufferUsage, &instr->bufusage_start);

    if (instr->need_walusage)
        WalUsageAccumDiff(&instr->walusage,
                          &pgWalUsage, &instr->walusage_start);

    /* Is this the first tuple of this cycle? */
    if (!instr->running)
    {
        instr->running = true;
        instr->firsttuple = INSTR_TIME_GET_DOUBLE(instr->counter);
    }
    else
    {
        /*
         * In async mode, if the plan node hadn't emitted any tuples before,
         * this might be the first tuple
         */
        if (instr->async_mode && save_tuplecount < 1.0)
            instr->firsttuple = INSTR_TIME_GET_DOUBLE(instr->counter);
    }
}

/* Update tuple count */
void
InstrUpdateTupleCount(Instrumentation *instr, double nTuples)
{
    /* count the returned tuples */
    instr->tuplecount += nTuples;
}

/* Finish a run cycle for a plan node */
void
InstrEndLoop(Instrumentation *instr)
{
    double      totaltime;

    /* Skip if nothing has happened, or already shut down */
    if (!instr->running)
        return;

    if (!INSTR_TIME_IS_ZERO(instr->starttime))
        elog(ERROR, "InstrEndLoop called on running node");

    /* Accumulate per-cycle statistics into totals */
    totaltime = INSTR_TIME_GET_DOUBLE(instr->counter);

    instr->startup += instr->firsttuple;
    instr->total += totaltime;
    instr->ntuples += instr->tuplecount;
    instr->nloops += 1;

    /* Reset for next cycle (if any) */
    instr->running = false;
    INSTR_TIME_SET_ZERO(instr->starttime);
    INSTR_TIME_SET_ZERO(instr->counter);
    instr->firsttuple = 0;
    instr->tuplecount = 0;
}

/* aggregate instrumentation information */
void
InstrAggNode(Instrumentation *dst, Instrumentation *add)
{
    if (!dst->running && add->running)
    {
        dst->running = true;
        dst->firsttuple = add->firsttuple;
    }
    else if (dst->running && add->running && dst->firsttuple > add->firsttuple)
        dst->firsttuple = add->firsttuple;

    INSTR_TIME_ADD(dst->counter, add->counter);

    dst->tuplecount += add->tuplecount;
    dst->startup += add->startup;
    dst->total += add->total;
    dst->ntuples += add->ntuples;
    dst->ntuples2 += add->ntuples2;
    dst->nloops += add->nloops;
    dst->nfiltered1 += add->nfiltered1;
    dst->nfiltered2 += add->nfiltered2;

    /* Add delta of buffer usage since entry to node's totals */
    if (dst->need_bufusage)
        BufferUsageAdd(&dst->bufusage, &add->bufusage);

    if (dst->need_walusage)
        WalUsageAdd(&dst->walusage, &add->walusage);
}

/* note current values during parallel executor startup */
void
InstrStartParallelQuery(void)
{
    save_pgBufferUsage = pgBufferUsage;
    save_pgWalUsage = pgWalUsage;
}

/* report usage after parallel executor shutdown */
void
InstrEndParallelQuery(BufferUsage *bufusage, WalUsage *walusage)
{
    memset(bufusage, 0, sizeof(BufferUsage));
    BufferUsageAccumDiff(bufusage, &pgBufferUsage, &save_pgBufferUsage);
    memset(walusage, 0, sizeof(WalUsage));
    WalUsageAccumDiff(walusage, &pgWalUsage, &save_pgWalUsage);
}

/* accumulate work done by workers in leader's stats */
void
InstrAccumParallelQuery(BufferUsage *bufusage, WalUsage *walusage)
{
    BufferUsageAdd(&pgBufferUsage, bufusage);
    WalUsageAdd(&pgWalUsage, walusage);
}

/* dst += add */
static void
BufferUsageAdd(BufferUsage *dst, const BufferUsage *add)
{
    dst->shared_blks_hit += add->shared_blks_hit;
    dst->shared_blks_read += add->shared_blks_read;
    dst->shared_blks_dirtied += add->shared_blks_dirtied;
    dst->shared_blks_written += add->shared_blks_written;
    dst->local_blks_hit += add->local_blks_hit;
    dst->local_blks_read += add->local_blks_read;
    dst->local_blks_dirtied += add->local_blks_dirtied;
    dst->local_blks_written += add->local_blks_written;
    dst->temp_blks_read += add->temp_blks_read;
    dst->temp_blks_written += add->temp_blks_written;
    INSTR_TIME_ADD(dst->blk_read_time, add->blk_read_time);
    INSTR_TIME_ADD(dst->blk_write_time, add->blk_write_time);
}

/* dst += add - sub */
void
BufferUsageAccumDiff(BufferUsage *dst,
                     const BufferUsage *add,
                     const BufferUsage *sub)
{
    dst->shared_blks_hit += add->shared_blks_hit - sub->shared_blks_hit;
    dst->shared_blks_read += add->shared_blks_read - sub->shared_blks_read;
    dst->shared_blks_dirtied += add->shared_blks_dirtied - sub->shared_blks_dirtied;
    dst->shared_blks_written += add->shared_blks_written - sub->shared_blks_written;
    dst->local_blks_hit += add->local_blks_hit - sub->local_blks_hit;
    dst->local_blks_read += add->local_blks_read - sub->local_blks_read;
    dst->local_blks_dirtied += add->local_blks_dirtied - sub->local_blks_dirtied;
    dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
    dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
    dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
    INSTR_TIME_ACCUM_DIFF(dst->blk_read_time,
                          add->blk_read_time, sub->blk_read_time);
    INSTR_TIME_ACCUM_DIFF(dst->blk_write_time,
                          add->blk_write_time, sub->blk_write_time);
}

/* helper functions for WAL usage accumulation */
static void
WalUsageAdd(WalUsage *dst, WalUsage *add)
{
    dst->wal_bytes += add->wal_bytes;
    dst->wal_records += add->wal_records;
    dst->wal_fpi += add->wal_fpi;
}

void
WalUsageAccumDiff(WalUsage *dst, const WalUsage *add, const WalUsage *sub)
{
    dst->wal_bytes += add->wal_bytes - sub->wal_bytes;
    dst->wal_records += add->wal_records - sub->wal_records;
    dst->wal_fpi += add->wal_fpi - sub->wal_fpi;
}