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Mutex: Add pthread mutex tunables

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This patch does not have any functionality change, we only provide a spin
count tunes for pthread adaptive spin mutex. The tunable
glibc.pthread.mutex_spin_count tunes can be used by system administrator to
squeeze system performance according to different hardware capabilities and
workload characteristics.

The maximum value of spin count is limited to 32767 to avoid the overflow
of mutex->__data.__spins variable with the possible type of short in
pthread_mutex_lock ().

The default value of spin count is set to 100 with the reference to the
previous number of times of spinning via trylock. This value would be
architecture-specific and can be tuned with kinds of benchmarks to fit most
cases in future.

I would extend my appreciation sincerely to H.J.Lu for his help to refine
this patch series.

	* manual/tunables.texi (POSIX Thread Tunables): New node.
	* nptl/Makefile (libpthread-routines): Add pthread_mutex_conf.
	* nptl/nptl-init.c: Include pthread_mutex_conf.h
	(__pthread_initialize_minimal_internal) [HAVE_TUNABLES]: Call
	 __pthread_tunables_init.
	* nptl/pthreadP.h (MAX_ADAPTIVE_COUNT): Remove.
	(max_adaptive_count): Define.
	* nptl/pthread_mutex_conf.c: New file.
	* nptl/pthread_mutex_conf.h: New file.
	* sysdeps/generic/adaptive_spin_count.h: New file.
	* sysdeps/nptl/dl-tunables.list: New file.
	* nptl/pthread_mutex_lock.c (__pthread_mutex_lock): Use
	max_adaptive_count () not MAX_ADAPTIVE_COUNT.
	* nptl/pthread_mutex_timedlock.c (__pthrad_mutex_timedlock):
	Likewise.

Suggested-by: Andi Kleen <andi.kleen@intel.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Kemi.wang <kemi.wang@intel.com>
This commit is contained in:
Kemi Wang 2018-12-01 07:03:33 -08:00 committed by H.J. Lu
parent 8e67b39eb4
commit 6310e6be9b
11 changed files with 190 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
ChangeLog
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@ -1,3 +1,21 @@
2018-12-01 Kemi Wang <kemi.wang@intel.com>
* manual/tunables.texi (POSIX Thread Tunables): New node.
* nptl/Makefile (libpthread-routines): Add pthread_mutex_conf.
* nptl/nptl-init.c: Include pthread_mutex_conf.h
(__pthread_initialize_minimal_internal) [HAVE_TUNABLES]: Call
__pthread_tunables_init.
* nptl/pthreadP.h (MAX_ADAPTIVE_COUNT): Remove.
(max_adaptive_count): Define.
* nptl/pthread_mutex_conf.c: New file.
* nptl/pthread_mutex_conf.h: New file.
* sysdeps/generic/adaptive_spin_count.h: New file.
* sysdeps/nptl/dl-tunables.list: New file.
* nptl/pthread_mutex_lock.c (__pthread_mutex_lock): Use
max_adaptive_count () not MAX_ADAPTIVE_COUNT.
* nptl/pthread_mutex_timedlock.c (__pthrad_mutex_timedlock):
Likewise.
2018-12-01 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #20544]

27
manual/tunables.texi
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@ -32,6 +32,7 @@ their own namespace.
* Tunable names:: The structure of a tunable name
* Memory Allocation Tunables:: Tunables in the memory allocation subsystem
* Elision Tunables:: Tunables in elision subsystem
* POSIX Thread Tunables:: Tunables in the POSIX thread subsystem
* Hardware Capability Tunables:: Tunables that modify the hardware
capabilities seen by @theglibc{}
@end menu
@ -281,6 +282,32 @@ of try lock attempts.
The default value of this tunable is @samp{3}.
@end deftp
@node POSIX Thread Tunables
@section POSIX Thread Tunables
@cindex pthread mutex tunables
@cindex thread mutex tunables
@cindex mutex tunables
@cindex tunables thread mutex
@deftp {Tunable namespace} glibc.pthread
The behavior of POSIX threads can be tuned to gain performance improvements
according to specific hardware capabilities and workload characteristics by
setting the following tunables in the @code{pthread} namespace:
@end deftp
@deftp Tunable glibc.pthread.mutex_spin_count
The @code{glibc.pthread.mutex_spin_count} tunable sets the maximum number of times
a thread should spin on the lock before calling into the kernel to block.
Adaptive spin is used for mutexes initialized with the
@code{PTHREAD_MUTEX_ADAPTIVE_NP} GNU extension. It affects both
@code{pthread_mutex_lock} and @code{pthread_mutex_timedlock}.
The thread spins until either the maximum spin count is reached or the lock
is acquired.
The default value of this tunable is @samp{100}.
@end deftp
@node Hardware Capability Tunables
@section Hardware Capability Tunables
@cindex hardware capability tunables

2
nptl/Makefile
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@ -145,7 +145,7 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
mtx_destroy mtx_init mtx_lock mtx_timedlock \
mtx_trylock mtx_unlock call_once cnd_broadcast \
cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait \
tss_create tss_delete tss_get tss_set
tss_create tss_delete tss_get tss_set pthread_mutex_conf
# pthread_setuid pthread_seteuid pthread_setreuid \
# pthread_setresuid \
# pthread_setgid pthread_setegid pthread_setregid \

5
nptl/nptl-init.c
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@ -38,6 +38,7 @@
#include <kernel-features.h>
#include <libc-pointer-arith.h>
#include <pthread-pids.h>
#include <pthread_mutex_conf.h>
#ifndef TLS_MULTIPLE_THREADS_IN_TCB
/* Pointer to the corresponding variable in libc. */
@ -431,6 +432,10 @@ __pthread_initialize_minimal_internal (void)
/* Determine whether the machine is SMP or not. */
__is_smp = is_smp_system ();
#if HAVE_TUNABLES
__pthread_tunables_init ();
#endif
}
strong_alias (__pthread_initialize_minimal_internal,
__pthread_initialize_minimal)

11
nptl/pthreadP.h
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@ -33,6 +33,7 @@
#include <kernel-features.h>
#include <errno.h>
#include <internal-signals.h>
#include "pthread_mutex_conf.h"
/* Atomic operations on TLS memory. */
@ -47,10 +48,14 @@
#endif
/* Adaptive mutex definitions. */
#ifndef MAX_ADAPTIVE_COUNT
# define MAX_ADAPTIVE_COUNT 100
static inline short max_adaptive_count (void)
{
#if HAVE_TUNABLES
return __mutex_aconf.spin_count;
#else
return DEFAULT_ADAPTIVE_COUNT;
#endif
}
/* Magic cookie representing robust mutex with dead owner. */

46
nptl/pthread_mutex_conf.c Normal file
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@ -0,0 +1,46 @@
/* Pthread mutex tunable parameters.
Copyright (C) 2018 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/>. */
#if HAVE_TUNABLES
# define TUNABLE_NAMESPACE pthread
#include <pthread_mutex_conf.h>
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
#include <elf/dl-tunables.h>
struct mutex_config __mutex_aconf =
{
/* The maximum number of times a thread should spin on the lock before
calling into kernel to block. */
.spin_count = DEFAULT_ADAPTIVE_COUNT,
};
static void
TUNABLE_CALLBACK (set_mutex_spin_count) (tunable_val_t *valp)
{
__mutex_aconf.spin_count = (int32_t) (valp)->numval;
}
void
__pthread_tunables_init (void)
{
TUNABLE_GET (mutex_spin_count, int32_t,
TUNABLE_CALLBACK (set_mutex_spin_count));
}
#endif

34
nptl/pthread_mutex_conf.h Normal file
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@ -0,0 +1,34 @@
/* Pthread mutex tunable parameters.
Copyright (C) 2018 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 _PTHREAD_MUTEX_CONF_H
#define _PTHREAD_MUTEX_CONF_H 1
#include <adaptive_spin_count.h>
#if HAVE_TUNABLES
struct mutex_config
{
int spin_count;
};
extern struct mutex_config __mutex_aconf attribute_hidden;
extern void __pthread_tunables_init (void) attribute_hidden;
#endif
#endif

2
nptl/pthread_mutex_lock.c
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@ -126,7 +126,7 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
if (LLL_MUTEX_TRYLOCK (mutex) != 0)
{
int cnt = 0;
int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
int max_cnt = MIN (max_adaptive_count (),
mutex->__data.__spins * 2 + 10);
do
{

2
nptl/pthread_mutex_timedlock.c
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@ -118,7 +118,7 @@ __pthread_mutex_timedlock (pthread_mutex_t *mutex,
if (lll_trylock (mutex->__data.__lock) != 0)
{
int cnt = 0;
int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
int max_cnt = MIN (max_adaptive_count (),
mutex->__data.__spins * 2 + 10);
do
{

22
sysdeps/generic/adaptive_spin_count.h Normal file
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@ -0,0 +1,22 @@
/* Maximum adaptive spin count by default
Copyright (C) 2018 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/>. */
/* The choice of 100 spins for the default spin count for an adaptive spin
is a completely arbitrary choice that has not been evaluated thoroughly
using modern hardware. */
#define DEFAULT_ADAPTIVE_COUNT 100

27
sysdeps/nptl/dl-tunables.list Normal file
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@ -0,0 +1,27 @@
# Copyright (C) 2018 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/>.
glibc {
pthread {
mutex_spin_count {
type: INT_32
minval: 0
maxval: 32767
default: 100
}
}
}