Messages in this thread | | | Date | Wed, 1 Jul 2009 17:44:51 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat |
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On Wed, Jul 01, 2009 at 09:53:04PM +0900, Hitoshi Mitake wrote: > From: Ingo Molnar <mingo@elte.hu> > Subject: Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat > Date: Wed, 1 Jul 2009 13:06:20 +0200 > > > > > * Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> wrote: > > > > > From: Ingo Molnar <mingo@elte.hu> > > > Subject: Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat > > > Date: Wed, 1 Jul 2009 11:07:49 +0200 > > > > > > > > > > > * Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> wrote: > > > > > > > > > From: Andi Kleen <andi@firstfloor.org> > > > > > Subject: Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat > > > > > Date: Wed, 01 Jul 2009 09:38:04 +0200 > > > > > > > > > > > Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> writes: > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > I wrote a test patch which add information of counts processes acquired how many spinlocks to schedstat. > > > > > > > After applied this patch, /proc/<PID>/sched will change like this, > > > > > > > > > > > > The problem is that spinlocks are very common and schedstats is > > > > > > enabled commonly in production kernels. You would need to > > > > > > demonstrate that such a change doesn't have significant > > > > > > performance impact. For me it looks like it has. > > > > > > > > > > I agree with your opinion about performance impact. > > > > > I thought this will make no problem, > > > > > because schedstat is categorized as "Kernel hacking" section. > > > > > But according to you, many production kernels enable it > > > > > so my patch will make widespread performance degradation. > > > > > I didn't know that, sorry. > > > > > > > > His arguments are bogus: both lockstat and perfcounters are optional > > > > (and default off), and the sw counter can be made near zero cost > > > > even if both perfcounters and lockstat is enabled. Also, sw counters > > > > are generally per CPU, etc. so not a performance issue. > > > > > > > > The only (small) overhead will be when the lock-acquire sw counter > > > > is actively enabled because you run 'perf stat -e lock-acquire' - > > > > but that is expected and inherent in pretty much any kind of > > > > instrumentation. > > > > > > > > The feature you are working on has the chance to be a very useful > > > > and popular piece of instrumentation. Being able to tell the lock > > > > acquire stats on a per task, per workload, per CPU or system-wide > > > > basis is a unique capability no other tool can offer right now. > > > > > > > > Andi is often trolling perfcounters related (and other) threads, > > > > please dont let yourself be deterred by that and feel free to ignore > > > > him. > > > OK, at least it is truth that > > > counter in perfcounters makes only valid overhead. > > > > > > And I have a question, > > > I tried to build perf, but I got a build error, > > > > > > util/symbol.c: In function ‘dso__load_sym’: > > > util/symbol.c:466: error: ‘ELF_C_READ_MMAP’ undeclared (first use in this function) > > > util/symbol.c:466: error: (Each undeclared identifier is reported only once > > > util/symbol.c:466: error: for each function it appears in.) > > > > > > I used this libelf, > > > http://www.mr511.de/software/english.html > > > but constant ELF_C_READ_MMAP is not provided... > > > > > > which "libelf" should I use? > > > It seems that there are some libelf implementations. > > > > I use the elfutils-libelf* packages: > > > > elfutils-libelf-devel-static-0.141-1.fc10.i386 > > elfutils-0.141-1.fc10.i386 > > elfutils-libelf-0.141-1.fc10.i386 > > elfutils-libs-0.141-1.fc10.i386 > > elfutils-libelf-devel-0.141-1.fc10.i386 > > > > do they work fine or you? > > I'm a Debian user, so I build this library from source > > https://fedorahosted.org/releases/e/l/elfutils/elfutils-0.141.tar.bz2 > > And I succeed to build perf, thanks!
You could also just
apt-get install libelf-dev
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