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Date: Tue, 26 Apr 2011 17:44:01 -0300
From: Arnaldo Carvalho de Melo <acme@...radead.org>
To: Lin Ming <ming.m.lin@...el.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>, Tim Blechmann <tim@...ngt.org>,
David Ahern <dsahern@...il.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH RFC] Fix per-task profiling Re: [PATCH] perf: Allow set
output buffer for tasks in the same thread group
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
View attachment "0001-perf-tools-Honour-the-cpu-list-parameter-when-also-m.patch" of type "text/plain" (1334 bytes)
View attachment "per_task_or_per_cpu_mmap.patch" of type "text/plain" (10115 bytes)
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