os_spin.c

00001 /*-
00002  * See the file LICENSE for redistribution information.
00003  *
00004  * Copyright (c) 1997, 1998, 1999, 2000
00005  * Sleepycat Software. All rights reserved.
00006  */
00007 
00008 #include "config.h"
00009 
00010 #ifndef lint
00011 static const char revid[] = "$Id: os__spin_8c-source.html,v 1.1 2008年06月08日 10:21:31 sebdiaz Exp $";
00012 #endif /* not lint */
00013 
00014 #ifndef NO_SYSTEM_INCLUDES
00015 #include <sys/types.h>
00016 #if defined(HAVE_PSTAT_GETDYNAMIC)
00017 #include <sys/pstat.h>
00018 #endif
00019 
00020 #include <limits.h>
00021 #include <unistd.h>
00022 #endif
00023 
00024 #include "db_int.h"
00025 #include "os_jump.h"
00026 
00027 #if defined(HAVE_PSTAT_GETDYNAMIC)
00028 /*
00029  * __os_pstat_getdynamic --
00030  * HP/UX.
00031  */
00032 static int
00033 __os_pstat_getdynamic()
00034 {
00035 struct pst_dynamic psd;
00036 
00037 return (pstat_getdynamic(&psd,
00038 sizeof(psd), (size_t)1, 0) == -1 ? 1 : psd.psd_proc_cnt);
00039 }
00040 #endif
00041 
00042 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
00043 /*
00044  * __os_sysconf --
00045  * Solaris, Linux.
00046  */
00047 static int
00048 __os_sysconf()
00049 {
00050 int nproc;
00051 
00052 return ((nproc = sysconf(_SC_NPROCESSORS_ONLN)) > 1 ? nproc : 1);
00053 }
00054 #endif
00055 
00056 /*
00057  * CDB___os_spin --
00058  * Return the number of default spins before blocking.
00059  *
00060  * PUBLIC: int CDB___os_spin __P((void));
00061  */
00062 int
00063 CDB___os_spin()
00064 {
00065 /*
00066  * If the application specified a value or we've already figured it
00067  * out, return it.
00068  *
00069  * XXX
00070  * We don't want to repeatedly call the underlying function because
00071  * it can be expensive (e.g., requiring multiple filesystem accesses
00072  * under Debian Linux).
00073  */
00074 if (DB_GLOBAL(db_tas_spins) != 0)
00075 return (DB_GLOBAL(db_tas_spins));
00076 
00077 DB_GLOBAL(db_tas_spins) = 1;
00078 #if defined(HAVE_PSTAT_GETDYNAMIC)
00079 DB_GLOBAL(db_tas_spins) = __os_pstat_getdynamic();
00080 #endif
00081 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
00082 DB_GLOBAL(db_tas_spins) = __os_sysconf();
00083 #endif
00084 
00085 /*
00086  * Spin 50 times per processor, we have anecdotal evidence that this
00087  * is a reasonable value.
00088  */
00089 if (DB_GLOBAL(db_tas_spins) != 1)
00090 DB_GLOBAL(db_tas_spins) *= 50;
00091 
00092 return (DB_GLOBAL(db_tas_spins));
00093 }
00094 
00095 /*
00096  * CDB___os_yield --
00097  * Yield the processor.
00098  *
00099  * PUBLIC: void CDB___os_yield __P((DB_ENV*, u_long));
00100  */
00101 void
00102 CDB___os_yield(dbenv, usecs)
00103 DB_ENV *dbenv;
00104 u_long usecs;
00105 {
00106 if (CDB___db_jump.j_yield != NULL && CDB___db_jump.j_yield() == 0)
00107 return;
00108 CDB___os_sleep(dbenv, 0, usecs);
00109 }