os_spin.c
上传用户:tsgydb
上传日期:2007-04-14
资源大小:10674k
文件大小:2k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1997, 1998, 1999, 2000
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: os_spin.c,v 11.5 2000/03/30 01:46:42 ubell Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #if defined(HAVE_PSTAT_GETDYNAMIC)
- #include <sys/pstat.h>
- #endif
- #include <limits.h>
- #include <unistd.h>
- #endif
- #include "db_int.h"
- #include "os_jump.h"
- #if defined(HAVE_PSTAT_GETDYNAMIC)
- /*
- * __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)
- /*
- * __os_sysconf --
- * Solaris, Linux.
- */
- static int
- __os_sysconf()
- {
- int nproc;
- return ((nproc = sysconf(_SC_NPROCESSORS_ONLN)) > 1 ? nproc : 1);
- }
- #endif
- /*
- * __os_spin --
- * Return the number of default spins before blocking.
- *
- * PUBLIC: int __os_spin __P((void));
- */
- int
- __os_spin()
- {
- /*
- * If the application specified a value or we've already figured it
- * out, return it.
- *
- * XXX
- * We don't want to repeatedly call the underlying function because
- * it can be expensive (e.g., requiring multiple filesystem accesses
- * under Debian Linux).
- */
- if (DB_GLOBAL(db_tas_spins) != 0)
- return (DB_GLOBAL(db_tas_spins));
- DB_GLOBAL(db_tas_spins) = 1;
- #if defined(HAVE_PSTAT_GETDYNAMIC)
- DB_GLOBAL(db_tas_spins) = __os_pstat_getdynamic();
- #endif
- #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
- DB_GLOBAL(db_tas_spins) = __os_sysconf();
- #endif
- /*
- * Spin 50 times per processor, we have anecdotal evidence that this
- * is a reasonable value.
- */
- if (DB_GLOBAL(db_tas_spins) != 1)
- DB_GLOBAL(db_tas_spins) *= 50;
- return (DB_GLOBAL(db_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_jump.j_yield != NULL && __db_jump.j_yield() == 0)
- return;
- __os_sleep(dbenv, 0, usecs);
- }