Messages in this thread | | | Date | Fri, 25 Feb 2011 00:46:40 +0900 | From | Hitoshi Mitake <> | Subject | Re: [PATCH] perf lock: clean the options for perf record |
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On 2011年02月23日 13:17, Hitoshi Mitake wrote: > On 2011年02月23日 03:22, Frederic Weisbecker wrote: >> On Tue, Feb 22, 2011 at 04:43:35PM +0100, Peter Zijlstra wrote: >>> On Wed, 2011-02-23 at 00:30 +0900, Hitoshi Mitake wrote: >>>> How do you think about it? >>> >>> Most of the lock code (esp the spinlock stuff) is already way over the >>> threshold of sanity, adding to that for some dubious reasons doesn't >>> seem like a good idea. >>> >>> I'm still not at all sure why people want all this lock tracing. >> >> Right, well I can imagine many usecases that could make lock >> tracing bring more value than what lockstat already provides, >> through a tool like perf lock if we enhance it. >> >> We should probably first focus on developing the tooling side >> and make it useful enough that optimizations in the kernel >> side become desirable. >> > > Yes, lockstat only provides the lock usage statistics of > entire of the system. perf lock will be able to provide the partial > information of specified term, or the degree of dependency > between locks. >
For trial, I created new tracepoint for rwsem and tested. Names of events are rwsem_{acquire, contended, acquired, release}, their meanings are similar to lock_{...}.
I traced perf bench sched messaging and result was,
mitake@x201i:~/linux/.../tools/perf% ./perf bench sched messaging # Running sched/messaging benchmark... # 20 sender and receiver processes per group # 10 groups == 400 processes run
Total time: 1.252 [sec] mitake@x201i:~/linux/.../tools/perf% sudo ./perf record -R -m 1024 -c 1 -e rwsem:rwsem_acquire -e rwsem:rwsem_release,rwsem:rwsem_contended,rwsem:rwsem_acquired ./perf bench sched messaging # Running sched/messaging benchmark... # 20 sender and receiver processes per group # 10 groups == 400 processes run
Total time: 1.332 [sec] [ perf record: Woken up 4 times to write data ] [ perf record: Captured and wrote 13.495 MB perf.data (~589597 samples) ]
raw execution of sched messaging was 1.252 sec, and traced version was 1.332 sec. This overhead is far smaller than the overhead of current lock tracepoints.
I think that it is possible to write some meaningful tools like reader/writer ratio measuring. If something can be written, I'll post it.
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