Messages in this thread | | | Date | Tue, 24 Mar 2015 17:12:11 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf record: Allow poll timeout to be specified |
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* David Ahern <david.ahern@oracle.com> 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. > > 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.
Please tune the default value (perhaps influenced by N_PROC?) so that users will get sane behavior without having to specify this option!
Thanks,
Ingo
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