1 /*- 2 * See the file LICENSE for redistribution information. 3 * 4 * Copyright (c) 1997, 1998 5 * Sleepycat Software. All rights reserved. 6 */ 7 8 #include "config.h" 9 10 #ifndef lint 11 static const char sccsid[] = "@(#)os_spin.c 10.10 (Sleepycat) 10/12/98"; 12 #endif /* not lint */ 13 14 #ifndef NO_SYSTEM_INCLUDES 15 #include <sys/types.h> 16 #if defined(HAVE_PSTAT_GETDYNAMIC) 17 #include <sys/pstat.h> 18 #endif 19 20 #include <limits.h> 21 #include <unistd.h> 22 #endif 23 24 #include "db_int.h" 25 #include "os_jump.h" 26 27 #if defined(HAVE_PSTAT_GETDYNAMIC) 28 /* 29 * __os_pstat_getdynamic -- 30 * HP/UX. 31 */ 32 static int 33 __os_pstat_getdynamic() 34 { 35 struct pst_dynamic psd; 36 37 return (pstat_getdynamic(&psd, 38 sizeof(psd), (size_t)1, 0) == -1 ? 1 : psd.psd_proc_cnt); 39 } 40 #endif 41 42 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN) 43 /* 44 * __os_sysconf -- 45 * Solaris, Linux. 46 */ 47 static int 48 __os_sysconf() 49 { 50 int nproc; 51 52 return ((nproc = sysconf(_SC_NPROCESSORS_ONLN)) > 1 ? nproc : 1); 53 } 54 #endif 55 56 /* 57 * __os_spin -- 58 * Return the number of default spins before blocking. 59 * 60 * PUBLIC: int __os_spin __P((void)); 61 */ 62 int 63 __os_spin() 64 { 65 /* 66 * If the application specified a value or we've already figured it 67 * out, return it. 68 * 69 * XXX 70 * We don't want to repeatedly call the underlying function because 71 * it can be expensive (e.g., requiring multiple filesystem accesses 72 * under Debian Linux). 73 */ 74 if (DB_GLOBAL(db_tsl_spins) != 0) 75 return (DB_GLOBAL(db_tsl_spins)); 76 77 DB_GLOBAL(db_tsl_spins) = 1; 78 #if defined(HAVE_PSTAT_GETDYNAMIC) 79 DB_GLOBAL(db_tsl_spins) = __os_pstat_getdynamic(); 80 #endif 81 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN) 82 DB_GLOBAL(db_tsl_spins) = __os_sysconf(); 83 #endif 84 85 /* 86 * Spin 50 times per processor, we have anecdotal evidence that this 87 * is a reasonable value. 88 */ 89 DB_GLOBAL(db_tsl_spins) *= 50; 90 91 return (DB_GLOBAL(db_tsl_spins)); 92 } 93 94 /* 95 * __os_yield -- 96 * Yield the processor. 97 * 98 * PUBLIC: void __os_yield __P((u_long)); 99 */ 100 void 101 __os_yield(usecs) 102 u_long usecs; 103 { 104 if (__db_jump.j_yield != NULL && __db_jump.j_yield() == 0) 105 return; 106 __os_sleep(0, usecs); 107 } 108