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Commit5cfa8dd

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Use mutex hint bit in PPC LWARX instructions, where possible.
The hint bit makes for a small but measurable performance improvementin access to contended spinlocks.On the other hand, some PPC chips give an illegal-instruction failure.There doesn't seem to be a completely bulletproof way to tell whether thehint bit will cause an illegal-instruction failure other than by tryingit; but most if not all 64-bit PPC machines should accept it, so followthe Linux kernel's lead and assume it's okay to use it in 64-bit builds.Of course we must also check whether the assembler accepts the command,since even with a recent CPU the toolchain could be old.Patch by Manabu Ori, significantly modified by me.
1 parent6b6137e commit5cfa8dd

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5 files changed

+104
-3
lines changed

5 files changed

+104
-3
lines changed

‎configure‎

Lines changed: 61 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1635,7 +1635,7 @@ Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
16351635
This configure script is free software; the Free Software Foundation
16361636
gives unlimited permission to copy, distribute and modify it.
16371637

1638-
Copyright (c) 1996-2011, PostgreSQL Global Development Group
1638+
Copyright (c) 1996-2012, PostgreSQL Global Development Group
16391639
_ACEOF
16401640
exit
16411641
fi
@@ -18207,6 +18207,66 @@ rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
1820718207
conftest$ac_exeext conftest.$ac_ext
1820818208
fi
1820918209

18210+
# On PPC, check if assembler supports LWARX instruction's mutex hint bit
18211+
case $host_cpu in
18212+
ppc*|powerpc*)
18213+
{ $as_echo "$as_me:$LINENO: checking whether assembler supports lwarx hint bit" >&5
18214+
$as_echo_n "checking whether assembler supports lwarx hint bit... " >&6; }
18215+
cat >conftest.$ac_ext <<_ACEOF
18216+
/* confdefs.h. */
18217+
_ACEOF
18218+
cat confdefs.h >>conftest.$ac_ext
18219+
cat >>conftest.$ac_ext <<_ACEOF
18220+
/* end confdefs.h. */
18221+
18222+
int
18223+
main ()
18224+
{
18225+
int a = 0; int *p = &a; int r;
18226+
__asm__ __volatile__ (" lwarx %0,0,%1,1\n" : "=&r"(r) : "r"(p));
18227+
;
18228+
return 0;
18229+
}
18230+
_ACEOF
18231+
rm -f conftest.$ac_objext
18232+
if { (ac_try="$ac_compile"
18233+
case "(($ac_try" in
18234+
*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
18235+
*) ac_try_echo=$ac_try;;
18236+
esac
18237+
eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
18238+
$as_echo "$ac_try_echo") >&5
18239+
(eval "$ac_compile") 2>conftest.er1
18240+
ac_status=$?
18241+
grep -v '^ *+' conftest.er1 >conftest.err
18242+
rm -f conftest.er1
18243+
cat conftest.err >&5
18244+
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
18245+
(exit $ac_status); } && {
18246+
test -z "$ac_c_werror_flag" ||
18247+
test ! -s conftest.err
18248+
} && test -s conftest.$ac_objext; then
18249+
pgac_cv_have_ppc_mutex_hint=yes
18250+
else
18251+
$as_echo "$as_me: failed program was:" >&5
18252+
sed 's/^/| /' conftest.$ac_ext >&5
18253+
18254+
pgac_cv_have_ppc_mutex_hint=no
18255+
fi
18256+
18257+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
18258+
{ $as_echo "$as_me:$LINENO: result: $pgac_cv_have_ppc_mutex_hint" >&5
18259+
$as_echo "$pgac_cv_have_ppc_mutex_hint" >&6; }
18260+
if test x"$pgac_cv_have_ppc_mutex_hint" = xyes ; then
18261+
18262+
cat >>confdefs.h <<\_ACEOF
18263+
#define HAVE_PPC_LWARX_MUTEX_HINT 1
18264+
_ACEOF
18265+
18266+
fi
18267+
;;
18268+
esac
18269+
1821018270
# Check largefile support. You might think this is a system service not a
1821118271
# compiler characteristic, but you'd be wrong. We must check this before
1821218272
# probing existence of related functions such as fseeko, since the largefile

‎configure.in‎

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1170,11 +1170,27 @@ if test "$with_krb5" = yes; then
11701170
AC_MSG_CHECKING(for krb5_free_unparsed_name)
11711171
AC_TRY_LINK([#include <krb5.h>],
11721172
[krb5_free_unparsed_name(NULL,NULL);],
1173-
[AC_DEFINE(HAVE_KRB5_FREE_UNPARSED_NAME, 1, [Define to 1 if you have krb5_free_unparsed_name])
1173+
[AC_DEFINE(HAVE_KRB5_FREE_UNPARSED_NAME, 1, [Define to 1 if you have krb5_free_unparsed_name.])
11741174
AC_MSG_RESULT(yes)],
11751175
[AC_MSG_RESULT(no)])
11761176
fi
11771177

1178+
# On PPC, check if assembler supports LWARX instruction's mutex hint bit
1179+
case $host_cpu in
1180+
ppc*|powerpc*)
1181+
AC_MSG_CHECKING([whether assembler supports lwarx hint bit])
1182+
AC_TRY_COMPILE([],
1183+
[int a = 0; int *p = &a; int r;
1184+
__asm__ __volatile__ (" lwarx %0,0,%1,1\n" : "=&r"(r) : "r"(p));],
1185+
[pgac_cv_have_ppc_mutex_hint=yes],
1186+
[pgac_cv_have_ppc_mutex_hint=no])
1187+
AC_MSG_RESULT([$pgac_cv_have_ppc_mutex_hint])
1188+
if test x"$pgac_cv_have_ppc_mutex_hint" = xyes ; then
1189+
AC_DEFINE(HAVE_PPC_LWARX_MUTEX_HINT, 1, [Define to 1 if the assembler supports PPC's LWARX mutex hint bit.])
1190+
fi
1191+
;;
1192+
esac
1193+
11781194
# Check largefile support. You might think this is a system service not a
11791195
# compiler characteristic, but you'd be wrong. We must check this before
11801196
# probing existence of related functions such as fseeko, since the largefile

‎src/include/pg_config.h.in‎

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -275,7 +275,7 @@
275275
/* Define to 1 if `text.data' is member of `krb5_error'. */
276276
#undef HAVE_KRB5_ERROR_TEXT_DATA
277277

278-
/* Define to 1 if you have krb5_free_unparsed_name */
278+
/* Define to 1 if you have krb5_free_unparsed_name. */
279279
#undef HAVE_KRB5_FREE_UNPARSED_NAME
280280

281281
/* Define to 1 if `client' is member of `krb5_ticket'. */
@@ -384,6 +384,9 @@
384384
/* Define to 1 if you have the POSIX signal interface. */
385385
#undef HAVE_POSIX_SIGNALS
386386

387+
/* Define to 1 if the assembler supports PPC's LWARX mutex hint bit. */
388+
#undef HAVE_PPC_LWARX_MUTEX_HINT
389+
387390
/* Define to 1 if you have the `pstat' function. */
388391
#undef HAVE_PSTAT
389392

‎src/include/pg_config_manual.h‎

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -6,6 +6,9 @@
66
* for developers.If you edit any of these, be sure to do a *full*
77
* rebuild (and an initdb if noted).
88
*
9+
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
10+
* Portions Copyright (c) 1994, Regents of the University of California
11+
*
912
* src/include/pg_config_manual.h
1013
*------------------------------------------------------------------------
1114
*/
@@ -170,6 +173,21 @@
170173
#definePG_PRINTF_ATTRIBUTE printf
171174
#endif
172175

176+
/*
177+
* On PPC machines, decide whether to use the mutex hint bit in LWARX
178+
* instructions. Setting the hint bit will slightly improve spinlock
179+
* performance on POWER6 and later machines, but does nothing before that,
180+
* and will result in illegal-instruction failures on some pre-POWER4
181+
* machines. By default we use the hint bit when building for 64-bit PPC,
182+
* which should be safe in nearly all cases. You might want to override
183+
* this if you are building 32-bit code for a known-recent PPC machine.
184+
*/
185+
#ifdefHAVE_PPC_LWARX_MUTEX_HINT/* must have assembler support in any case */
186+
#if defined(__ppc64__)|| defined(__powerpc64__)
187+
#defineUSE_PPC_LWARX_MUTEX_HINT
188+
#endif
189+
#endif
190+
173191
/*
174192
*------------------------------------------------------------------------
175193
* The following symbols are for enabling debugging code, not for

‎src/include/storage/s_lock.h‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -372,7 +372,11 @@ tas(volatile slock_t *lock)
372372
int_res;
373373

374374
__asm__ __volatile__(
375+
#ifdefUSE_PPC_LWARX_MUTEX_HINT
376+
"lwarx %0,0,%3,1\n"
377+
#else
375378
"lwarx %0,0,%3\n"
379+
#endif
376380
"cmpwi %0,0\n"
377381
"bne 1f\n"
378382
"addi %0,%0,1\n"

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