1 /*-
2 * See the file LICENSE for redistribution information.
3 *
4 * Copyright (c) 1997, 1998, 1999
5 * Sleepycat Software. All rights reserved.
6 */
7
8 #include "db_config.h"
9
10 #ifndef lint
11 static const char sccsid[] = "@(#)os_spin.c 11.2 (Sleepycat) 11/3/99";
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
22 #ifndef _MSC_VER /* _WIN32 */
23 #include <unistd.h>
24 #endif
25
26 #endif
27
28 #include "db_int.h"
29 #include "os_jump.h"
30
31 #if defined(HAVE_PSTAT_GETDYNAMIC)
32 /*
33 * __os_pstat_getdynamic --
34 * HP/UX.
35 */
36 static int
__os_pstat_getdynamic()37 __os_pstat_getdynamic()
38 {
39 struct pst_dynamic psd;
40
41 return (pstat_getdynamic(&psd,
42 sizeof(psd), (size_t)1, 0) == -1 ? 1 : psd.psd_proc_cnt);
43 }
44 #endif
45
46 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
47 /*
48 * CDB___os_sysconf --
49 * Solaris, Linux.
50 */
51 static int
CDB___os_sysconf()52 CDB___os_sysconf()
53 {
54 int nproc;
55
56 return ((nproc = sysconf(_SC_NPROCESSORS_ONLN)) > 1 ? nproc : 1);
57 }
58 #endif
59
60 /*
61 * CDB___os_spin --
62 * Return the number of default spins before blocking.
63 *
64 * PUBLIC: int CDB___os_spin __P((void));
65 */
66 int
CDB___os_spin()67 CDB___os_spin()
68 {
69 /*
70 * If the application specified a value or we've already figured it
71 * out, return it.
72 *
73 * XXX
74 * We don't want to repeatedly call the underlying function because
75 * it can be expensive (e.g., requiring multiple filesystem accesses
76 * under Debian Linux).
77 */
78 if (DB_GLOBAL(db_tas_spins) != 0)
79 return (DB_GLOBAL(db_tas_spins));
80
81 DB_GLOBAL(db_tas_spins) = 1;
82 #if defined(HAVE_PSTAT_GETDYNAMIC)
83 DB_GLOBAL(db_tas_spins) = __os_pstat_getdynamic();
84 #endif
85 #if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
86 DB_GLOBAL(db_tas_spins) = CDB___os_sysconf();
87 #endif
88
89 /*
90 * Spin 50 times per processor, we have anecdotal evidence that this
91 * is a reasonable value.
92 */
93 if (DB_GLOBAL(db_tas_spins) != 1)
94 DB_GLOBAL(db_tas_spins) *= 50;
95
96 return (DB_GLOBAL(db_tas_spins));
97 }
98
99 /*
100 * CDB___os_yield --
101 * Yield the processor.
102 *
103 * PUBLIC: void CDB___os_yield __P((u_long));
104 */
105 void
CDB___os_yield(usecs)106 CDB___os_yield(usecs)
107 u_long usecs;
108 {
109 if (CDB___db_jump.j_yield != NULL && CDB___db_jump.j_yield() == 0)
110 return;
111 CDB___os_sleep(0, usecs);
112 }
113