Messages in this thread | | | Date | Thu, 11 Jun 2015 12:45:44 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH V2 1/1] perf,tools: add time out to force stop endless mmap processing |
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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
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