lkml.org 
[lkml]   [2015]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V2 1/1] perf,tools: add time out to force stop endless mmap processing
    Em Thu, Jun 11, 2015 at 03:49:04AM -0400, kan.liang@intel.com escreveu:
    > perf top reads all threads' /proc/xxx/maps. If there is any threads
    > which generating a keeping growing huge /proc/xxx/maps, perf will do
    > infinite loop in perf_event__synthesize_mmap_events.
    > This patch fixes this issue by adding a time out to force stop this kind
    > of endless mmap processing.
    >
    > Reported-by: Huang, Ying <ying.huang@intel.com>
    > Signed-off-by: Kan Liang <kan.liang@intel.com>
    >
    > ---
    >
    > Changes since V1
    > - Add warning message for time out.

    <SNIP>

    > + if ((rdclock() - t) > MMAP_TIMEOUT) {
    > + pr_warning("Reading %s time out."
    > + "The file may be too huge or keep growing.\n",
    > + filename);
    > + break;
    > + }
    > +
    > /* ensure null termination since stack will be reused. */
    > strcpy(execname, "");

    Have you tried this? I.e. pr_warning, IIRC, will make it appear in the
    logs that this happened, but this will get probably lost in the noise
    and only if you have a suspicion that something may have went wrong you
    will try to look in the, possibly long, logs for a possible explanation.

    So, perhaps we need to do something like what is done in
    perf_session__process_events(), i.e. at the end of the synthesizing,
    look at a counter for such situations and use ui__warning(), that in the
    TUI case will show a window message that will show the warning and wait
    for the user to acknowledge it by pressing a Ok button.

    This is all done in perf_session__warn_about_errors().

    This is how I think this should be done, but as this is such a corner
    case, and this patch fixes these long loops, this may be applied now and
    then what I suggest may be done on top.

    Anyway, please try to reply to David Ahern question about an example for
    this case, because he is working on a netlink based replacement to the
    synthesizing of PERF_RECORD_ events for existing tasks and will have to
    take this case into account there as well...

    - Arnaldo


    \
     
     \ /
      Last update: 2015-06-11 18:01    [W:3.393 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site