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powerpc: Add the lock elision using HTM
This patch adds support for lock elision using ISA 2.07 hardware transactional memory instructions for pthread_mutex primitives. Similar to s390 version, the for elision logic defined in 'force-elision.h' is only enabled if ENABLE_LOCK_ELISION is defined. Also, the lock elision code should be able to be built even with a compiler that does not provide HTM support with builtins. However I have noted the performance is sub-optimal due scheduling pressures.
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Adhemerval Zanella
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Jan 12, 2015
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| /* elision-conf.c: Lock elision tunable parameters. | ||
| Copyright (C) 2014 Free Software Foundation, Inc. | ||
| This file is part of the GNU C Library. | ||
| The GNU C Library is free software; you can redistribute it and/or | ||
| modify it under the terms of the GNU Lesser General Public | ||
| License as published by the Free Software Foundation; either | ||
| version 2.1 of the License, or (at your option) any later version. | ||
| The GNU C Library is distributed in the hope that it will be useful, | ||
| but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| Lesser General Public License for more details. | ||
| You should have received a copy of the GNU Lesser General Public | ||
| License along with the GNU C Library; if not, see | ||
| <http://www.gnu.org/licenses/>. */ | ||
|
|
||
| #include "config.h" | ||
| #include <pthreadP.h> | ||
| #include <elision-conf.h> | ||
| #include <unistd.h> | ||
| #include <dl-procinfo.h> | ||
|
|
||
| /* Reasonable initial tuning values, may be revised in the future. | ||
| This is a conservative initial value. */ | ||
|
|
||
| struct elision_config __elision_aconf = | ||
| { | ||
| /* How many times to use a non-transactional lock after a transactional | ||
| failure has occurred because the lock is already acquired. Expressed | ||
| in number of lock acquisition attempts. */ | ||
| .skip_lock_busy = 3, | ||
| /* How often to not attempt to use elision if a transaction aborted due | ||
| to reasons other than other threads' memory accesses. Expressed in | ||
| number of lock acquisition attempts. */ | ||
| .skip_lock_internal_abort = 3, | ||
| /* How often to not attempt to use elision if a lock used up all retries | ||
| without success. Expressed in number of lock acquisition attempts. */ | ||
| .skip_lock_out_of_tbegin_retries = 3, | ||
| /* How often we retry using elision if there is chance for the transaction | ||
| to finish execution (e.g., it wasn't aborted due to the lock being | ||
| already acquired. */ | ||
| .try_tbegin = 3, | ||
| /* Same as SKIP_LOCK_INTERNAL_ABORT but for trylock. */ | ||
| .skip_trylock_internal_abort = 3, | ||
| }; | ||
|
|
||
| /* Force elision for all new locks. This is used to decide whether existing | ||
| DEFAULT locks should be automatically use elision in pthread_mutex_lock(). | ||
| Disabled for suid programs. Only used when elision is available. */ | ||
|
|
||
| int __pthread_force_elision attribute_hidden; | ||
|
|
||
| /* Initialize elision. */ | ||
|
|
||
| static void | ||
| elision_init (int argc __attribute__ ((unused)), | ||
| char **argv __attribute__ ((unused)), | ||
| char **environ) | ||
| { | ||
| #ifdef ENABLE_LOCK_ELISION | ||
| int elision_available = (GLRO (dl_hwcap2) & PPC_FEATURE2_HAS_HTM) ? 1 : 0; | ||
| __pthread_force_elision = __libc_enable_secure ? 0 : elision_available; | ||
| #endif | ||
| } | ||
|
|
||
| #ifdef SHARED | ||
| # define INIT_SECTION ".init_array" | ||
| # define MAYBE_CONST | ||
| #else | ||
| # define INIT_SECTION ".preinit_array" | ||
| # define MAYBE_CONST const | ||
| #endif | ||
|
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||
| void (*MAYBE_CONST __pthread_init_array []) (int, char **, char **) | ||
| __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) = | ||
| { | ||
| &elision_init | ||
| }; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| /* elision-conf.h: Lock elision tunable parameters. | ||
| Copyright (C) 2014 Free Software Foundation, Inc. | ||
| This file is part of the GNU C Library. | ||
| The GNU C Library is free software; you can redistribute it and/or | ||
| modify it under the terms of the GNU Lesser General Public | ||
| License as published by the Free Software Foundation; either | ||
| version 2.1 of the License, or (at your option) any later version. | ||
| The GNU C Library is distributed in the hope that it will be useful, | ||
| but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| Lesser General Public License for more details. | ||
| You should have received a copy of the GNU Lesser General Public | ||
| License along with the GNU C Library; if not, see | ||
| <http://www.gnu.org/licenses/>. */ | ||
|
|
||
| #ifndef _ELISION_CONF_H | ||
| #define _ELISION_CONF_H 1 | ||
|
|
||
| #include <pthread.h> | ||
| #include <time.h> | ||
|
|
||
| /* Should make sure there is no false sharing on this. */ | ||
| struct elision_config | ||
| { | ||
| int skip_lock_busy; | ||
| int skip_lock_internal_abort; | ||
| int skip_lock_out_of_tbegin_retries; | ||
| int try_tbegin; | ||
| int skip_trylock_internal_abort; | ||
| } __attribute__ ((__aligned__ (128))); | ||
|
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| extern struct elision_config __elision_aconf attribute_hidden; | ||
|
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| extern int __pthread_force_elision attribute_hidden; | ||
|
|
||
| /* Tell the test suite to test elision for this architecture. */ | ||
| #define HAVE_ELISION 1 | ||
|
|
||
| #endif |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| /* elision-lock.c: Elided pthread mutex lock. | ||
| Copyright (C) 2014 Free Software Foundation, Inc. | ||
| This file is part of the GNU C Library. | ||
| The GNU C Library is free software; you can redistribute it and/or | ||
| modify it under the terms of the GNU Lesser General Public | ||
| License as published by the Free Software Foundation; either | ||
| version 2.1 of the License, or (at your option) any later version. | ||
| The GNU C Library is distributed in the hope that it will be useful, | ||
| but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| Lesser General Public License for more details. | ||
| You should have received a copy of the GNU Lesser General Public | ||
| License along with the GNU C Library; if not, see | ||
| <http://www.gnu.org/licenses/>. */ | ||
|
|
||
| #include <stdio.h> | ||
| #include <pthread.h> | ||
| #include <pthreadP.h> | ||
| #include <lowlevellock.h> | ||
| #include <elision-conf.h> | ||
| #include "htm.h" | ||
|
|
||
| /* PowerISA 2.0.7 Section B.5.5 defines isync to be insufficient as a | ||
| barrier in acquire mechanism for HTM operations, a strong 'sync' is | ||
| required. */ | ||
| #undef __arch_compare_and_exchange_val_32_acq | ||
| #define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \ | ||
| ({ \ | ||
| __typeof (*(mem)) __tmp; \ | ||
| __typeof (mem) __memp = (mem); \ | ||
| __asm __volatile ( \ | ||
| "1: lwarx %0,0,%1" MUTEX_HINT_ACQ "\n" \ | ||
| " cmpw %0,%2\n" \ | ||
| " bne 2f\n" \ | ||
| " stwcx. %3,0,%1\n" \ | ||
| " bne- 1b\n" \ | ||
| "2: sync" \ | ||
| : "=&r" (__tmp) \ | ||
| : "b" (__memp), "r" (oldval), "r" (newval) \ | ||
| : "cr0", "memory"); \ | ||
| __tmp; \ | ||
| }) | ||
|
|
||
| #if !defined(LLL_LOCK) && !defined(EXTRAARG) | ||
| /* Make sure the configuration code is always linked in for static | ||
| libraries. */ | ||
| #include "elision-conf.c" | ||
| #endif | ||
|
|
||
| #ifndef EXTRAARG | ||
| # define EXTRAARG | ||
| #endif | ||
| #ifndef LLL_LOCK | ||
| # define LLL_LOCK(a,b) lll_lock(a,b), 0 | ||
| #endif | ||
|
|
||
| #define aconf __elision_aconf | ||
|
|
||
| /* Adaptive lock using transactions. | ||
| By default the lock region is run as a transaction, and when it | ||
| aborts or the lock is busy the lock adapts itself. */ | ||
|
|
||
| int | ||
| __lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared) | ||
| { | ||
| if (*adapt_count > 0) | ||
| { | ||
| (*adapt_count)--; | ||
| goto use_lock; | ||
| } | ||
|
|
||
| int try_begin = aconf.try_tbegin; | ||
| while (1) | ||
| { | ||
| if (__builtin_tbegin (0)) | ||
| { | ||
| if (*lock == 0) | ||
| return 0; | ||
| /* Lock was busy. Fall back to normal locking. */ | ||
| __builtin_tabort (_ABORT_LOCK_BUSY); | ||
| } | ||
| else | ||
| { | ||
| /* A persistent failure indicates that a retry will probably | ||
| result in another failure. Use normal locking now and | ||
| for the next couple of calls. */ | ||
| if (try_begin-- <= 0 | ||
| || _TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) | ||
| { | ||
| if (aconf.skip_lock_internal_abort > 0) | ||
| *adapt_count = aconf.skip_lock_internal_abort; | ||
| goto use_lock; | ||
| } | ||
| /* Same logic as above, but for for a number of temporary failures | ||
| in a row. */ | ||
| else if (aconf.skip_lock_out_of_tbegin_retries > 0 | ||
| && aconf.try_tbegin > 0) | ||
| *adapt_count = aconf.skip_lock_out_of_tbegin_retries; | ||
| } | ||
| } | ||
|
|
||
| use_lock: | ||
| return LLL_LOCK ((*lock), pshared); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,28 @@ | ||
| /* elision-timed.c: Lock elision timed lock. | ||
| Copyright (C) 2014 Free Software Foundation, Inc. | ||
| This file is part of the GNU C Library. | ||
| The GNU C Library is free software; you can redistribute it and/or | ||
| modify it under the terms of the GNU Lesser General Public | ||
| License as published by the Free Software Foundation; either | ||
| version 2.1 of the License, or (at your option) any later version. | ||
| The GNU C Library is distributed in the hope that it will be useful, | ||
| but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| Lesser General Public License for more details. | ||
| You should have received a copy of the GNU Lesser General Public | ||
| License along with the GNU C Library; if not, see | ||
| <http://www.gnu.org/licenses/>. */ | ||
|
|
||
| #include <time.h> | ||
| #include <elision-conf.h> | ||
| #include "lowlevellock.h" | ||
|
|
||
| #define __lll_lock_elision __lll_timedlock_elision | ||
| #define EXTRAARG const struct timespec *t, | ||
| #undef LLL_LOCK | ||
| #define LLL_LOCK(a, b) lll_timedlock(a, t, b) | ||
|
|
||
| #include "elision-lock.c" |
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