0edbf12301
Current allocate_stack logic for create stacks is to first mmap all
the required memory with the desirable memory and then mprotect the
guard area with PROT_NONE if required. Although it works as expected,
it pessimizes the allocation because it requires the kernel to actually
increase commit charge (it counts against the available physical/swap
memory available for the system).
The only issue is to actually check this change since side-effects are
really Linux specific and to actually account them it would require a
kernel specific tests to parse the system wide information. On the kernel
I checked /proc/self/statm does not show any meaningful difference for
vmm and/or rss before and after thread creation. I could only see
really meaningful information checking on system wide /proc/meminfo
between thread creation: MemFree, MemAvailable, and Committed_AS shows
large difference without the patch. I think trying to use these
kind of information on a testcase is fragile.
The BZ#18988 reports shows that the commit pages are easily seen with
mlockall (MCL_FUTURE) (with lock all pages that become mapped in the
process) however a more straighfoward testcase shows that pthread_create
could be faster using this patch:
--
static const int inner_count = 256;
static const int outer_count = 128;
static
void *thread1(void *arg)
{
return NULL;
}
static
void *sleeper(void *arg)
{
pthread_t ts[inner_count];
for (int i = 0; i < inner_count; i++)
pthread_create (&ts[i], &a, thread1, NULL);
for (int i = 0; i < inner_count; i++)
pthread_join (ts[i], NULL);
return NULL;
}
int main(void)
{
pthread_attr_init(&a);
pthread_attr_setguardsize(&a, 1<<20);
pthread_attr_setstacksize(&a, 1134592);
pthread_t ts[outer_count];
for (int i = 0; i < outer_count; i++)
pthread_create(&ts[i], &a, sleeper, NULL);
for (int i = 0; i < outer_count; i++)
pthread_join(ts[i], NULL);
assert(r == 0);
}
return 0;
}
--
On x86_64 (4.4.0-45-generic, gcc 5.4.0) running the small benchtests
I see:
$ time ./test
real 0m3.647s
user 0m0.080s
sys 0m11.836s
While with the patch I see:
$ time ./test
real 0m0.696s
user 0m0.040s
sys 0m1.152s
So I added a pthread_create benchtest (thread_create) which check
the thread creation latency. As for the simple benchtests, I saw
improvements in thread creation on all architectures I tested the
change.
Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
arm-linux-gnueabihf, powerpc64le-linux-gnu, sparc64-linux-gnu,
and sparcv9-linux-gnu.
[BZ #18988]
* benchtests/thread_create-inputs: New file.
* benchtests/thread_create-source.c: Likewise.
* support/xpthread_attr_setguardsize.c: Likewise.
* support/Makefile (libsupport-routines): Add
xpthread_attr_setguardsize object.
* support/xthread.h: Add xpthread_attr_setguardsize prototype.
* benchtests/Makefile (bench-pthread): Add thread_create.
* nptl/allocatestack.c (allocate_stack): Call mmap with PROT_NONE and
then mprotect the required area.
80 lines
3.4 KiB
C
80 lines
3.4 KiB
C
/* Support functionality for using threads.
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Copyright (C) 2016-2017 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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#ifndef SUPPORT_THREAD_H
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#define SUPPORT_THREAD_H
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#include <pthread.h>
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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/* Terminate the process (with exit status 0) after SECONDS have
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elapsed, from a helper thread. The process is terminated with the
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exit function, so atexit handlers are executed. */
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void delayed_exit (int seconds);
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/* Terminate the process (with exit status 1) if VALUE is not zero.
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In that case, print a failure message to standard output mentioning
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FUNCTION. The process is terminated with the exit function, so
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atexit handlers are executed. */
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void xpthread_check_return (const char *function, int value);
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/* The following functions call the corresponding libpthread functions
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and terminate the process on error. */
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void xpthread_barrier_init (pthread_barrier_t *barrier,
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pthread_barrierattr_t *attr, unsigned int count);
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void xpthread_barrier_destroy (pthread_barrier_t *barrier);
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void xpthread_mutexattr_destroy (pthread_mutexattr_t *);
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void xpthread_mutexattr_init (pthread_mutexattr_t *);
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void xpthread_mutexattr_setprotocol (pthread_mutexattr_t *, int);
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void xpthread_mutexattr_setpshared (pthread_mutexattr_t *, int);
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void xpthread_mutexattr_setrobust (pthread_mutexattr_t *, int);
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void xpthread_mutexattr_settype (pthread_mutexattr_t *, int);
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void xpthread_mutex_init (pthread_mutex_t *, const pthread_mutexattr_t *);
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void xpthread_mutex_destroy (pthread_mutex_t *);
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void xpthread_mutex_lock (pthread_mutex_t *mutex);
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void xpthread_mutex_unlock (pthread_mutex_t *mutex);
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void xpthread_mutex_consistent (pthread_mutex_t *);
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void xpthread_spin_lock (pthread_spinlock_t *lock);
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void xpthread_spin_unlock (pthread_spinlock_t *lock);
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void xpthread_cond_wait (pthread_cond_t * cond, pthread_mutex_t * mutex);
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pthread_t xpthread_create (pthread_attr_t *attr,
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void *(*thread_func) (void *), void *closure);
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void xpthread_detach (pthread_t thr);
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void xpthread_cancel (pthread_t thr);
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void *xpthread_join (pthread_t thr);
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void xpthread_once (pthread_once_t *guard, void (*func) (void));
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void xpthread_attr_destroy (pthread_attr_t *attr);
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void xpthread_attr_init (pthread_attr_t *attr);
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void xpthread_attr_setdetachstate (pthread_attr_t *attr,
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int detachstate);
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void xpthread_attr_setstacksize (pthread_attr_t *attr,
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size_t stacksize);
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void xpthread_attr_setguardsize (pthread_attr_t *attr,
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size_t guardsize);
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/* This function returns non-zero if pthread_barrier_wait returned
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PTHREAD_BARRIER_SERIAL_THREAD. */
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int xpthread_barrier_wait (pthread_barrier_t *barrier);
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__END_DECLS
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#endif /* SUPPORT_THREAD_H */
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