• Arnaldo Carvalho de Melo's avatar
    perf evlist: Fix per thread mmap setup · aece948f
    Arnaldo Carvalho de Melo authored
    The PERF_EVENT_IOC_SET_OUTPUT ioctl was returning -EINVAL when using
    --pid when monitoring multithreaded apps, as we can only share a ring
    buffer for events on the same thread if not doing per cpu.
    
    Fix it by using per thread ring buffers.
    
    Tested with:
    
    [root@felicio ~]# 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@felicio ~]#
    
    So 11 threads under pid 26131, then:
    
    [root@felicio ~]# perf record -F 50000 --pid 26131
    
    [root@felicio ~]# 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@felicio ~]#
    
    11 mmaps, one per thread since we didn't specify any CPU list, so we need one
    mmap per thread and:
    
    [root@felicio ~]# 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@felicio ~]# 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@felicio ~]#
    
    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@felicio ~]# 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@felicio ~]# 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@felicio ~]#
    
    This machine has two cores, so fewer threads appeared on the radar, and:
    
    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
     1 7f484b922000-7f484b9a3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    [root@felicio ~]#
    
    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@felicio ~]# 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@felicio ~]# 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@felicio ~]#
    
    It uses per-cpu buffers.
    
    For just one thread:
    
    [root@felicio ~]# 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@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl
         1	   9969 26148
    [root@felicio ~]#
    
    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
         1	7f286a51b000-7f286a59c000 rwxs 00000000 00:09 4064                       anon_inode:[perf_event]
    [root@felicio ~]#
    Tested-by: default avatarDavid Ahern <dsahern@gmail.com>
    Tested-by: default avatarLin Ming <ming.m.lin@intel.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Tom Zanussi <tzanussi@gmail.com>
    Link: http://lkml.kernel.org/r/20110426204401.GB1746@ghostprotocols.netSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    aece948f
evlist.h 2.05 KB