os_spin.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: os_spin.c,v 12.3 2005/08/10 15:47:27 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#if defined(HAVE_PSTAT_GETDYNAMIC)
#include <sys/pstat.h>
#endif

#include <limits.h>                     /* Needed for sysconf on Solaris. */
#endif

#include "db_int.h"

#if defined(HAVE_PSTAT_GETDYNAMIC)
static int __os_pstat_getdynamic __P((void));

/*
 * __os_pstat_getdynamic --
 *      HP/UX.
 */
static int
__os_pstat_getdynamic()
{
        struct pst_dynamic psd;

        return (pstat_getdynamic(&psd,
            sizeof(psd), (size_t)1, 0) == -1 ? 1 : psd.psd_proc_cnt);
}
#endif

#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
static u_int32_t __os_sysconf __P((void));

/*
 * __os_sysconf --
 *      Solaris, Linux.
 */
static u_int32_t
__os_sysconf()
{
        long nproc;

        nproc = sysconf(_SC_NPROCESSORS_ONLN);
        return ((u_int32_t)(nproc > 1 ? nproc : 1));
}
#endif

/*
 * __os_spin --
 *      Set the number of default spins before blocking.
 *
 * PUBLIC: u_int32_t __os_spin __P((DB_ENV *));
 */
u_int32_t
__os_spin(dbenv)
        DB_ENV *dbenv;
{
        u_int32_t tas_spins;

        COMPQUIET(dbenv, NULL);

        tas_spins = 1;
#if defined(HAVE_PSTAT_GETDYNAMIC)
        tas_spins = __os_pstat_getdynamic();
#endif
#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
        tas_spins = __os_sysconf();
#endif

        /*
         * Spin 50 times per processor, we have anecdotal evidence that this
         * is a reasonable value.
         */
        if (tas_spins != 1)
                tas_spins *= 50;

        return (tas_spins);
}

/*
 * __os_yield --
 *      Yield the processor.
 *
 * PUBLIC: void __os_yield __P((DB_ENV*, u_long));
 */
void
__os_yield(dbenv, usecs)
        DB_ENV *dbenv;
        u_long usecs;
{
        if (DB_GLOBAL(j_yield) != NULL && DB_GLOBAL(j_yield)() == 0)
                return;
#ifdef HAVE_VXWORKS
        taskDelay(1);
#endif
        __os_sleep(dbenv, 0, usecs);
}

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