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Date: Mon, 16 Apr 2012 14:10:30 +0000 From: "Chen, Dennis (SRDC SW)" <Dennis1.Chen@....com> To: Ingo Molnar <mingo@...nel.org> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>, "peterz@...radead.org" <peterz@...radead.org>, Paul Mackerras <paulus@...ba.org>, Arnaldo Carvalho de Melo <acme@...stprotocols.net> Subject: RE: [PATCH 0/2] tools perf: Add a new benchmark tool for semaphore/mutex On Mon, Apr 16, 2012 at 5:24 PM, Ingo Molnar <mingo@...nel.org> wrote: > > * Chen, Dennis (SRDC SW) <Dennis1.Chen@....com> wrote: > >> <PATCH PREFACE> >> ------------------- >> This patch series are used to add a new performance benchmark tool for semaphore or mutex: >> The new tool will fork NR tasks specified through the command line and bind each of them >> to every CPUs in the system equally. The command to launch the tool looks like: >> '# perf bench locking mutex -p 8 -t 400 -c' >> >> The above command will create 400 tasks in a system with 8-CPU, each CPU will have 50 tasks. >> After the task be created, it will read all the files and directories in '/sys/module'. >> sysfs is RAM based and its read operation for both dir and file is very sensitive for mutex >> lock, also '/sys/module' has almost no dependencies on external devices. >> >> We can use this tool with 'perf record' command to get the hot-spot of the codes or >> 'perf top -g' to get live info, for example, below is a test case run in a intel i7-2600 box >> (-c option is to get the cpu cycles, I don't use it in this test case): >> >> # perf record -a perf bench locking mutex -p 8 -t 4000 >> # Running locking/mutex benchmark... >> ... >> [13894 ]/6 duration 23 s 609392 us >> [13996 ]/4 duration 23 s 599418 us >> [14056 ]/0 duration 23 s 595710 us >> [13715 ]/3 duration 23 s 621719 us >> [13390 ]/6 duration 23 s 644020 us >> [13696 ]/0 duration 23 s 623101 us >> [14334 ]/6 duration 23 s 580262 us >> [14343 ]/7 duration 23 s 578702 us >> [14283 ]/3 duration 23 s 583007 us >> ----------------------------------- >> Total duration 79353 s 943945 us >> >> real: 23.84 s >> user: 0.00 >> sys: 0.45 >> >> # perf report >> =================================================================================== >> ... >> # perf version : 3.3.2 >> # arch : x86_64 >> # nrcpus online : 8 >> # nrcpus avail : 8 >> # cpudesc : Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz >> # total memory : 3966460 kB >> # cmdline : /usr/bin/perf record -a perf bench locking mutex -p 8 -t 4000 >> >> # Events: 131K cycles >> # >> # Overhead Command Shared Object Symbol >> # ........ ............... ................................. ..................................... >> # >> 22.12% perf [kernel.kallsyms] [k] __mutex_lock_slowpath >> 8.27% perf [kernel.kallsyms] [k] _raw_spin_lock >> 6.16% perf [kernel.kallsyms] [k] mutex_unlock >> 5.22% perf [kernel.kallsyms] [k] mutex_spin_on_owner >> 4.94% perf [kernel.kallsyms] [k] sysfs_refresh_inode >> 4.82% perf [kernel.kallsyms] [k] mutex_lock >> 2.67% perf [kernel.kallsyms] [k] __mutex_unlock_slowpath >> 2.61% perf [kernel.kallsyms] [k] link_path_walk >> 2.42% perf [kernel.kallsyms] [k] _raw_spin_lock_irqsave >> 1.61% perf [kernel.kallsyms] [k] __d_lookup >> 1.18% perf [kernel.kallsyms] [k] clear_page_c >> 1.16% perf [kernel.kallsyms] [k] dput >> 0.97% perf [kernel.kallsyms] [k] do_lookup >> 0.93% swapper [kernel.kallsyms] [k] intel_idle >> 0.87% perf [kernel.kallsyms] [k] get_page_from_freelist >> 0.85% perf [kernel.kallsyms] [k] __strncpy_from_user >> 0.81% perf [kernel.kallsyms] [k] system_call >> 0.78% perf libc-2.13.so [.] 0x84ef0 >> 0.71% perf [kernel.kallsyms] [k] vfsmount_lock_local_lock >> 0.68% perf [kernel.kallsyms] [k] sysfs_dentry_revalidate >> 0.62% perf [kernel.kallsyms] [k] try_to_wake_up >> 0.62% perf [kernel.kallsyms] [k] kfree >> 0.60% perf [kernel.kallsyms] [k] kmem_cache_alloc >> ............................................................................................ >> > > Nice! Would be nice to lift some of this information over into > the changelogs, to address my complaints in the previous mail. Thanks for the suggestion! I will resubmit the patches into a single patch and include the above info to address the changelog issue... >> We can see that for 4000 tasks running in 8 CPUs simultaneously, it will create a very heavy >> contention for the mutex lock, so lot's of tasks enter into the slow path of the mutex lock... >> I am very curious if we switch the mutex to the semaphore in this case, how's thing going? >> My next plan > > Seems like an unfinished sentence. Oh, I mean my next plan is to do some performance analysis of the 2 primitives with this tool... > Thanks, > > Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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