Messages in this thread | | | Date | Wed, 25 Mar 2015 13:38:55 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf record: Allow poll timeout to be specified |
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On Tue, Mar 24, 2015 at 12:09:48PM -0400, David Ahern wrote: > Record currently wakes up based on watermarks to read events from the mmaps and > write them out to the file. The result is a file that can have large blocks of > events per mmap before a finished round event is added to the stream. This in > turn affects the quantity of events that have to be passed through the ordered > events queue before results can be displayed to the user. For commands like > perf-script this can lead to long unnecessarily long delays before a user gets > output. Large systems (e.g, 1024 cpus) further compound this effect. I have seen > instances where I have to wait 45 minutes for perf-script to process a 5GB file > before any events are shown.
so you have pipe to perf script, right?
> > This patch adds an option to perf-record to allow a user to specify the > poll timeout in msec. For example using 100 msec timeouts similar to perf-top > means the mmaps are traversed much more frequently leading to a smoother > analysis side.
there's also the '--no-buffering' option that sets:
attr->watermark = 0; attr->wakeup_events = 1;
but that's just the other edge, which is not what you'd want
I think it's good to have user side configurable as well
Acked-by: Jiri Olsa <jolsa@kernel.org>
thanks, jirka
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