pg_rusage.c

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/*-------------------------------------------------------------------------
 *
 * pg_rusage.c
 *    Resource usage measurement support routines.
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/misc/pg_rusage.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <unistd.h>

#include "utils/pg_rusage.h"


/*
 * Initialize usage snapshot.
 */
void
pg_rusage_init(PGRUsage *ru0)
{
    getrusage(RUSAGE_SELF, &ru0->ru);
    gettimeofday(&ru0->tv, NULL);
}

/*
 * Compute elapsed time since ru0 usage snapshot, and format into
 * a displayable string.  Result is in a static string, which is
 * tacky, but no one ever claimed that the Postgres backend is
 * threadable...
 */
const char *
pg_rusage_show(const PGRUsage *ru0)
{
    static char result[100];
    PGRUsage    ru1;

    pg_rusage_init(&ru1);

    if (ru1.tv.tv_usec < ru0->tv.tv_usec)
    {
        ru1.tv.tv_sec--;
        ru1.tv.tv_usec += 1000000;
    }
    if (ru1.ru.ru_stime.tv_usec < ru0->ru.ru_stime.tv_usec)
    {
        ru1.ru.ru_stime.tv_sec--;
        ru1.ru.ru_stime.tv_usec += 1000000;
    }
    if (ru1.ru.ru_utime.tv_usec < ru0->ru.ru_utime.tv_usec)
    {
        ru1.ru.ru_utime.tv_sec--;
        ru1.ru.ru_utime.tv_usec += 1000000;
    }

    snprintf(result, sizeof(result),
             "CPU %d.%02ds/%d.%02du sec elapsed %d.%02d sec",
             (int) (ru1.ru.ru_stime.tv_sec - ru0->ru.ru_stime.tv_sec),
          (int) (ru1.ru.ru_stime.tv_usec - ru0->ru.ru_stime.tv_usec) / 10000,
             (int) (ru1.ru.ru_utime.tv_sec - ru0->ru.ru_utime.tv_sec),
          (int) (ru1.ru.ru_utime.tv_usec - ru0->ru.ru_utime.tv_usec) / 10000,
             (int) (ru1.tv.tv_sec - ru0->tv.tv_sec),
             (int) (ru1.tv.tv_usec - ru0->tv.tv_usec) / 10000);

    return result;
}