+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]
* 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
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
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 \
#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. */
/* 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)
#include <kernel-features.h>
#include <errno.h>
#include <internal-signals.h>
+#include "pthread_mutex_conf.h"
/* Atomic operations on TLS memory. */
#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. */
--- /dev/null
+/* 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
--- /dev/null
+/* 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
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
{
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
{
--- /dev/null
+/* 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
--- /dev/null
+# 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
+ }
+ }
+}