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9695cb3e65
This patch optimizes powerpc spinlock implementation by: * Use the correct EH hint bit on the larx for supported ISA. For lock acquisition, the thread that acquired the lock with a successful stcx does not want to give away the write ownership on the cacheline. The idea is to make the load reservation "sticky" about retaining write authority to the line. That way, the store that must inevitably come to release the lock can succeed quickly and not contend with other threads issuing lwarx. If another thread does a store to the line (false sharing), the winning thread must give up write authority to the proper value of EH for the larx for a lock acquisition is 1. * Increase contented lock performance by up to 40%, and no measurable impact on uncontended locks on P8. Thanks to Adhemerval Zanella who did most of the work. I've run some tests, and addressed some minor feedback. * sysdeps/powerpc/nptl/pthread_spin_lock.c (pthread_spin_lock): Add lwarx hint, and use macro for acquire instruction. * sysdeps/powerpc/nptl/pthread_spin_trylock.c (pthread_spin_trylock): Likewise. * sysdep/unix/sysv/linux/powerpc/pthread_spin_unlock.c: Move to ... * sysdeps/powerpc/nptl/pthread_spin_unlock.c: ... here, and update to use new atomic macros.
42 lines
1.3 KiB
C
42 lines
1.3 KiB
C
/* Copyright (C) 2003-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
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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 <errno.h>
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#include "pthreadP.h"
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int
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pthread_spin_trylock (pthread_spinlock_t *lock)
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{
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unsigned int old;
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int err = EBUSY;
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asm ("1: lwarx %0,0,%2" MUTEX_HINT_ACQ "\n"
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" cmpwi 0,%0,0\n"
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" bne 2f\n"
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" stwcx. %3,0,%2\n"
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" bne- 1b\n"
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" li %1,0\n"
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__ARCH_ACQ_INSTR "\n"
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"2: "
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: "=&r" (old), "=&r" (err)
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: "r" (lock), "r" (1), "1" (err)
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: "cr0", "memory");
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return err;
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}
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