• Arnaldo Carvalho de Melo's avatar
    perf beauty waitid options: Fix up prefix showing logic · 8b4fdbce
    Arnaldo Carvalho de Melo authored
    [ Upstream commit 1da7e002 ]
    
    When introducing the possibility for selecting if the common prefix to
    options such as the waitid ones, i.e. all 'waitid' options start with
    'W', so, to make it make it more compact if configured to suppress it,
    'perf trace' will do so, other examples include mmap's PROT_ prefix for
    its 'prot' argument, etc, which, when showing the syscall argument name
    ends up producing duplicated info that clutters the screen, i.e.:
    
      # perf trace -e mmap --max-events 2 sleep 1
         0.000 ( 0.014 ms): sleep/20886 mmap(len: 112595, prot: PROT_READ, flags: MAP_PRIVATE, fd: 3) = 0x7f3e986d2000
         0.041 ( 0.005 ms): sleep/20886 mmap(len: 8192, prot: PROT_READ|PROT_WRITE, flags: MAP_PRIVATE|MAP_ANONYMOUS) = 0x7f3e986d0000
      #
    
    So it is possible to suppress that and make it more compact by having
    this in your ~/.perfconfig:
    
      # cat ~/.perfconfig
      [trace]
    	show_prefix = no
      #
    
      # perf trace -e mmap --max-events 2 sleep 1
         0.000 ( 0.014 ms): sleep/8009 mmap(len: 112595, prot: READ, flags: PRIVATE, fd: 3) = 0x7ff2373de000
         0.040 ( 0.005 ms): sleep/8009 mmap(len: 8192, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS) = 0x7ff2373dc000
      #
    
    To have it look more like strace's output, we instead want to suppress
    the arg name and show the prefix, so use:
    
      # cat ~/.perfconfig
      [trace]
    	show_prefix = yes
    	show_arg_names = no
      #
      # perf trace -e mmap --max-events 2 sleep 1
         0.000 ( 0.006 ms): sleep/15513 mmap(NULL, 112595, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7a9b6d3000
         0.020 ( 0.002 ms): sleep/15513 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS) = 0x7f7a9b6d1000
      #
    
    When this logic was introduced a bug came with it when processing the
    waitid 'option' arg that ended up expecting 3 strings when just two were
    being provided, fix it.
    
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Wang Nan <wangnan0@huawei.com>
    Fixes: c65c83ff ("perf trace: Allow asking for not suppressing common string prefixes")
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    8b4fdbce
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