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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997, 1998
* Sleepycat Software. All rights reserved.
*/
#include "config.h"
#ifndef lint
static const char sccsid[] = "@(#)os_spin.c 10.7 (Sleepycat) 5/20/98";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <limits.h>
#include <unistd.h>
#endif
#include "db_int.h"
/*
* __os_spin --
* Return the number of default spins before blocking.
*
* PUBLIC: int __os_spin __P((void));
*/
int
__os_spin()
{
static long sys_val;
/* If the application specified the spins, use its value. */
if (DB_GLOBAL(db_tsl_spins) != 0)
return (DB_GLOBAL(db_tsl_spins));
/* If we've already figured this out, return the value. */
if (sys_val != 0)
return (sys_val);
/*
* XXX
* Solaris and Linux use _SC_NPROCESSORS_ONLN to return the number of
* online processors. We don't want to repeatedly call sysconf because
* it's quite expensive (requiring multiple filesystem accesses) under
* Debian Linux.
*
* Spin 50 times per processor -- we have anecdotal evidence that this
* is a reasonable value.
*/
#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
if ((sys_val = sysconf(_SC_NPROCESSORS_ONLN)) > 1)
sys_val *= 50;
else
sys_val = 1;
#else
sys_val = 1;
#endif
return (sys_val);
}
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