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Re: [PATCH v8] Mutex: Add pthread mutex tunables

On 2018年07月17日 19:21, H.J. Lu wrote:
> On Mon, Jul 9, 2018 at 6:17 PM, 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 30000 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.
>>    * sysdeps/nptl/dl-tunables.list: Add glibc.pthread.mutex_spin_count entry.
>>    * manual/tunables.texi: Add glibc.pthread.mutex_spin_count description.
>>    * sysdeps/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: Move MAX_ADAPTIVE_COUNT macro definition to
>>      pthread_mutex_conf.h
>> I would extend my appreciation sincerely to H.J.Lu for his help to refine
>> this patch series.
>> ChangeLog:
>>         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)
>> Reviewed-by: Carlos O'Donell <>
>> Suggested-by: Andi Kleen <>
>> Signed-off-by: <>


> Thanks.

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