• Arnaldo Carvalho de Melo's avatar
    perf core: Allow setting up max frame stack depth via sysctl · c5dfd78e
    Arnaldo Carvalho de Melo authored
    The default remains 127, which is good for most cases, and not even hit
    most of the time, but then for some cases, as reported by Brendan, 1024+
    deep frames are appearing on the radar for things like groovy, ruby.
    And in some workloads putting a _lower_ cap on this may make sense. One
    that is per event still needs to be put in place tho.
    The new file is:
      # cat /proc/sys/kernel/perf_event_max_stack
    Chaging it:
      # echo 256 > /proc/sys/kernel/perf_event_max_stack
      # cat /proc/sys/kernel/perf_event_max_stack
    But as soon as there is some event using callchains we get:
      # echo 512 > /proc/sys/kernel/perf_event_max_stack
      -bash: echo: write error: Device or resource busy
    Because we only allocate the callchain percpu data structures when there
    is a user, which allows for changing the max easily, its just a matter
    of having no callchain users at that point.
    Reported-and-Tested-by: default avatarBrendan Gregg <brendan.d.gregg@gmail.com>
    Reviewed-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: He Kuang <hekuang@huawei.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Milian Wolff <milian.wolff@kdab.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Cc: Wang Nan <wangnan0@huawei.com>
    Cc: Zefan Li <lizefan@huawei.com>
    Link: http://lkml.kernel.org/r/20160426002928.GB16708@kernel.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
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