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Date: Tue, 26 Apr 2011 15:28:45 -0600 From: David Ahern <dsahern@...il.com> To: Arnaldo Carvalho de Melo <acme@...radead.org> CC: Lin Ming <ming.m.lin@...el.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Ingo Molnar <mingo@...e.hu>, Tim Blechmann <tim@...ngt.org>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH RFC] Fix per-task profiling Re: [PATCH] perf: Allow set output buffer for tasks in the same thread group On 04/26/11 14:44, Arnaldo Carvalho de Melo wrote: > Em Mon, Apr 25, 2011 at 12:28:33PM -0300, Arnaldo Carvalho de Melo escreveu: >> Em Mon, Apr 25, 2011 at 09:40:38PM +0800, Lin Ming escreveu: >>> On Mon, 2011-04-25 at 01:05 +0800, Peter Zijlstra wrote: >>>> On Sun, 2011-04-24 at 22:57 +0800, Lin Ming wrote: >>>>> Currently, kernel only allows an event to redirect its output to other >>>>> events of the same task. > >>>>> This causes PERF_EVENT_IOC_SET_OUTPUT ioctl fails when an event is >>>>> trying to redirect its output to other events in the same thread group. > >>>> Which is exactly what it should do, you should never be allowed to >>>> redirect your events to that of another task, since that other task >>>> might be running on another CPU. > >>>> The buffer code strictly assumes no concurrency, therefore its either >>>> one task or one CPU. > >>> Well, this is not the right fix, then the perf tool code need to be >>> fixed. > >> Yes, I'm working on it. > > Lin, David, Tim, can you please try the two patches attached? > > Tested with: > > [root@...icio ~]# tuna -t 26131 -CP | nl > 1 thread ctxt_switches > 2 pid SCHED_ rtpri affinity voluntary nonvoluntary cmd > 3 26131 OTHER 0 0,1 10814276 2397830 chromium-browse > 4 642 OTHER 0 0,1 14688 0 chromium-browse > 5 26148 OTHER 0 0,1 713602 115479 chromium-browse > 6 26149 OTHER 0 0,1 801958 2262 chromium-browse > 7 26150 OTHER 0 0,1 1271128 248 chromium-browse > 8 26151 OTHER 0 0,1 3 0 chromium-browse > 9 27049 OTHER 0 0,1 36796 9 chromium-browse > 10 618 OTHER 0 0,1 14711 0 chromium-browse > 11 661 OTHER 0 0,1 14593 0 chromium-browse > 12 29048 OTHER 0 0,1 28125 0 chromium-browse > 13 26143 OTHER 0 0,1 2202789 781 chromium-browse > [root@...icio ~]# > > So 11 threads under pid 26131, then: > > [root@...icio ~]# perf record -F 50000 --pid 26131 > > [root@...icio ~]# grep perf_event /proc/`pidof perf`/maps | nl > 1 7fa4a2538000-7fa4a25b9000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 2 7fa4a25b9000-7fa4a263a000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 3 7fa4a263a000-7fa4a26bb000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 4 7fa4a26bb000-7fa4a273c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 5 7fa4a273c000-7fa4a27bd000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 6 7fa4a27bd000-7fa4a283e000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 7 7fa4a283e000-7fa4a28bf000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 8 7fa4a28bf000-7fa4a2940000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 9 7fa4a2940000-7fa4a29c1000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 10 7fa4a29c1000-7fa4a2a42000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 11 7fa4a2a42000-7fa4a2ac3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > [root@...icio ~]# > > 11 mmaps, one per thread since we didn't specify any CPU list, so we need one > mmap per thread and: > > [root@...icio ~]# perf record -F 50000 --pid 26131 > ^M > ^C[ perf record: Woken up 79 times to write data ] > [ perf record: Captured and wrote 20.614 MB perf.data (~900639 samples) ] > > [root@...icio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl > 1 371310 26131 > 2 96516 26148 > 3 95694 26149 > 4 95203 26150 > 5 7291 26143 > 6 87 27049 > 7 76 661 > 8 60 29048 > 9 47 618 > 10 43 642 > [root@...icio ~]# > > Ok, one of the threads, 26151 was quiescent, so no samples there, but all the > others are there. > > Then, if I specify one CPU: > > [root@...icio ~]# perf record -F 50000 --pid 26131 --cpu 1 > ^C[ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.680 MB perf.data (~29730 samples) ] > > [root@...icio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl > 1 8444 26131 > 2 2584 26149 > 3 2518 26148 > 4 2324 26150 > 5 123 26143 > 6 9 661 > 7 9 29048 > [root@...icio ~]# > > This machine has two cores, so fewer threads appeared on the radar, and: > > [root@...icio ~]# grep perf_event /proc/`pidof perf`/maps | nl > 1 7f484b922000-7f484b9a3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > [root@...icio ~]# > > Just one mmap, as now we can use just one per-cpu buffer instead of the > per-thread needed in the previous case. > > For global profiling: > > [root@...icio ~]# perf record -F 50000 -a > ^C[ perf record: Woken up 26 times to write data ] > [ perf record: Captured and wrote 7.128 MB perf.data (~311412 samples) ] > > [root@...icio ~]# grep perf_event /proc/`pidof perf`/maps | nl > 1 7fb49b435000-7fb49b4b6000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > 2 7fb49b4b6000-7fb49b537000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > [root@...icio ~]# > > It uses per-cpu buffers. > > For just one thread: > > [root@...icio ~]# perf record -F 50000 --tid 26148 > ^C[ perf record: Woken up 2 times to write data ] > [ perf record: Captured and wrote 0.330 MB perf.data (~14426 samples) ] > > [root@...icio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl > 1 9969 26148 > [root@...icio ~]# > > [root@...icio ~]# grep perf_event /proc/`pidof perf`/maps | nl > 1 7f286a51b000-7f286a59c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event] > [root@...icio ~]# > > Can you guys please test it and provide Tested-by and/or Acked-by? > > Thanks, > > - Arnaldo Worked for me (KVM process). Tested-by: David Ahern dsahern@...il.com -- 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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