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With TLE enabled, the adapt count variable update incurs an 8% overhead before entering the critical section of an elided mutex. Instead, if it is done right after leaving the critical section, this serialization can be avoided. This alters the existing behavior of __lll_trylock_elision as it will only decrement the adapt_count if it successfully acquires the lock. * sysdeps/unix/sysv/linux/powerpc/elision-lock.c (__lll_lock_elision): Remove adapt_count decrement... * sysdeps/unix/sysv/linux/powerpc/elision-trylock.c (__lll_trylock_elision): Likewise. * sysdeps/unix/sysv/linux/powerpc/elision-unlock.c (__lll_unlock_elision): ... to here. And utilize new adapt_count parameter. * sysdeps/unix/sysv/linux/powerpc/lowlevellock.h (__lll_unlock_elision): Update to include adapt_count parameter. (lll_unlock_elision): Pass pointer to adapt_count variable.
41 lines
1.4 KiB
C
41 lines
1.4 KiB
C
/* elision-unlock.c: Commit an elided pthread lock.
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Copyright (C) 2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include "pthreadP.h"
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#include "lowlevellock.h"
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#include "htm.h"
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int
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__lll_unlock_elision (int *lock, short *adapt_count, int pshared)
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{
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/* When the lock was free we're in a transaction. */
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if (*lock == 0)
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__builtin_tend (0);
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else
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{
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lll_unlock ((*lock), pshared);
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/* Update the adapt count AFTER completing the critical section.
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Doing this here prevents unneeded stalling when entering
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a critical section. Saving about 8% runtime on P8. */
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if (*adapt_count > 0)
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(*adapt_count)--;
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}
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return 0;
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}
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