This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH v10] Mutex: Add pthread mutex tunables
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Kemi Wang <kemi dot wang at intel dot com>, Glibc alpha <libc-alpha at sourceware dot org>
- Date: Fri, 30 Nov 2018 17:03:22 -0500
- Subject: Re: [PATCH v10] Mutex: Add pthread mutex tunables
- References: <1543565573-1419-1-git-send-email-kemi.wang@intel.com>
On 11/30/18 3:12 AM, Kemi Wang wrote:
> 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.
OK for master with the comment in adaptive_spin_count.h fixed.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> * sysdeps/nptl/dl-tunables.list: Add glibc.pthread.mutex_spin_count entry.
> * manual/tunables.texi: Add glibc.pthread.mutex_spin_count description.
> * nptl/pthread_mutex_conf.h: New file.
> * nptl/pthread_mutex_conf.c: New file.
> * nptl/Makefile: Add pthread_mutex_conf.c for compilation.
> * nptl/nptl-init.c: Put pthread mutex tunable initialization in pthread
> initialization.
> * nptl/pthreadP.h: Add a new function max_adaptive_count() to get the
> maximum adaptive spin value.
> * sysdeps/generic/adaptive_spin_count.h: Move DEFAULT_ADAPTIVE_COUNT
> macro to a generic header.
> * nptl/pthread_mutex_lock.c: Replace MAX_ADAPTIVE_COUNT by
> max_adaptive_count().
> * nptl/pthread_mutex_timedlock.c: Replace MAX_ADAPTIVE_COUNT by
> max_adaptive_count().
>
> I would extend my appreciation sincerely to H.J.Lu for his help to refine
> this patch series.
>
> ChangeLog:
> V9->V10:
> a) Remove superfluous comments, as suggested by Adhemerval Zanella
> b) Use max_adaptive_count() to get the maximum spin count, as suggested
> by Adhemerval Zanella
> c) Move DEFAULT_ADAPTIVE_COUNT definition to a generic header and
> override this header by the architecture in future, as suggested by
> Adhemerval Zanella
> d) Use macro DEFAULT_ADAPTIVE_COUNT to replace magic number 100, as
> suggested by Carlos
> e) Other minor change on tunable description, as suggested by Carlos
> f) Change maximum value of adaptive spin count from 30000 to 32767(full
> short range), as suggested by Adhemerval Zanella.
> g) Move "struct mutex_config" definition back to pthread_mutex_conf.h,
> thus, the header pthreadP.h does not have to be included in
> pthread_mutex_conf.c
>
> V8->V9:
> a) Add the "unistd.h" header file back, or it will cause build
> regression on 32 bits system.
> b) Rebase on the latest master branch
> c) Tested on x86_64 with build-many-glibcs.py
>
> V7->V8:
> a) Refine the pthread tunables description in manual/tunables.texi
> accordingly to Carlos O'Donell and Rical Jason.
>
> V6->V7:
> a) Patch is refined by H.J.Lu
>
> V5->V6:
> a) Missing "pthread mutex tunables" entry in the menu of tunables.texi,
> add it.
>
> V4->V5
> a) Put mutex tunable (glibc.mutex.spin_count) initialization as part of
> overall pthread initialization, that would avoid the extra relocation,
> as suggested by Florian Weimer. Thanks for pointing it out!
> b) Move the READ_ONLY_SPIN macro definition from the third patch to
> this patch
>
> V3->V4
> a) Add comments in elf/dl-tunables.list
>
> V2->V3
> a) Polish the description of glibc.mutex.spin_count tunable with the
> help from Rical Jasan.
> b) Get rid of the TUNABLE_CALLBACK_FNDECL macros in
> pthread_mutex_conf.c, as suggested by Florian Weimer.
> c) Adjust the default value of spin count to 100 with the reference of
> the previous spinning way via trylock.
>
> V1->V2
> a) Renamed nptl/mutex-conf.h -> nptl/pthread_mutex_conf.h
> b) Renamed nptl/mutex-conf.c -> nptl/pthread_mutex_conf.c
> c) Change the Makefile to compile pthread_mutex_conf.c
> d) Modify the copyright "2013-2018" -> "2018" for new added files
> e) Fix the indentation issue (tab -> double space) in
> elf/dl-tunables.list
> f) Remove the env alias LD_SPIN_COUNT in elf/dl-tunables.list
> g) Fix the typo errors and refresh glibc.mutex.spin_count tunable
> description in manual/tunables.texi.
> h) Fix the indentation issue in nptl/pthread_mutex_conf.c
> i) Fix the indentation issue for nested preprocessor (add one space for
> each level)
>
> Suggested-by: Andi Kleen <andi.kleen@intel.com>
> Signed-off-by: Kemi.wang <kemi.wang@intel.com>
> ---
> manual/tunables.texi | 27 +++++++++++++++++++++
> nptl/Makefile | 2 +-
> nptl/nptl-init.c | 5 ++++
> nptl/pthreadP.h | 11 ++++++---
> nptl/pthread_mutex_conf.c | 45 +++++++++++++++++++++++++++++++++++
> nptl/pthread_mutex_conf.h | 34 ++++++++++++++++++++++++++
> nptl/pthread_mutex_lock.c | 2 +-
> nptl/pthread_mutex_timedlock.c | 2 +-
> sysdeps/generic/adaptive_spin_count.h | 22 +++++++++++++++++
> sysdeps/nptl/dl-tunables.list | 27 +++++++++++++++++++++
> 10 files changed, 171 insertions(+), 6 deletions(-)
> create mode 100644 nptl/pthread_mutex_conf.c
> create mode 100644 nptl/pthread_mutex_conf.h
> create mode 100644 sysdeps/generic/adaptive_spin_count.h
> create mode 100644 sysdeps/nptl/dl-tunables.list
>
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index 3345a23..09a2565 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -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
OK.
> * 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:
OK.
> +@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}.
OK.
> +@end deftp
> +
> @node Hardware Capability Tunables
> @section Hardware Capability Tunables
> @cindex hardware capability tunables
> diff --git a/nptl/Makefile b/nptl/Makefile
> index 49b6faa..284f815 100644
> --- a/nptl/Makefile
> +++ b/nptl/Makefile
> @@ -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
OK.
> # pthread_setuid pthread_seteuid pthread_setreuid \
> # pthread_setresuid \
> # pthread_setgid pthread_setegid pthread_setregid \
> diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
> index 907411d..adf99f1 100644
> --- a/nptl/nptl-init.c
> +++ b/nptl/nptl-init.c
> @@ -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
OK.
> }
> strong_alias (__pthread_initialize_minimal_internal,
> __pthread_initialize_minimal)
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 19efe1e..7f16ba9 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -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;
OK.
> #endif
> +}
>
>
> /* Magic cookie representing robust mutex with dead owner. */
> diff --git a/nptl/pthread_mutex_conf.c b/nptl/pthread_mutex_conf.c
> new file mode 100644
> index 0000000..612981a
> --- /dev/null
> +++ b/nptl/pthread_mutex_conf.c
> @@ -0,0 +1,45 @@
> +/* 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
OK.
> diff --git a/nptl/pthread_mutex_conf.h b/nptl/pthread_mutex_conf.h
> new file mode 100644
> index 0000000..945eff8
> --- /dev/null
> +++ b/nptl/pthread_mutex_conf.h
> @@ -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);
> +#endif
> +
> +#endif
OK.
> diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
> index 29cc143..474b4df 100644
> --- a/nptl/pthread_mutex_lock.c
> +++ b/nptl/pthread_mutex_lock.c
> @@ -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 (),
OK.
> mutex->__data.__spins * 2 + 10);
> do
> {
> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
> index 888c12f..453b824 100644
> --- a/nptl/pthread_mutex_timedlock.c
> +++ b/nptl/pthread_mutex_timedlock.c
> @@ -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 (),
OK.
> mutex->__data.__spins * 2 + 10);
> do
> {
> diff --git a/sysdeps/generic/adaptive_spin_count.h b/sysdeps/generic/adaptive_spin_count.h
> new file mode 100644
> index 0000000..48c8d9b
> --- /dev/null
> +++ b/sysdeps/generic/adaptive_spin_count.h
> @@ -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. */
Fix comment style to use GNU style, and fixing indent.
e.g.
/* 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
> diff --git a/sysdeps/nptl/dl-tunables.list b/sysdeps/nptl/dl-tunables.list
> new file mode 100644
> index 0000000..beebd5a
> --- /dev/null
> +++ b/sysdeps/nptl/dl-tunables.list
> @@ -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
OK.
> + }
> + }
> +}
>
--
Cheers,
Carlos.