Re: [PATCH v10] Mutex: Add pthread mutex tunables

[Carlos O'Donell <carlos at redhat dot 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.