Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 6 Oct 2020 10:28:35 +0900 | Subject | Re: [PATCH] perf inject: Flush ordered events on FINISHED_ROUND |
| |
Hi Jiri,
On Mon, Oct 5, 2020 at 4:52 AM Jiri Olsa <jolsa@redhat.com> wrote: > > On Fri, Oct 02, 2020 at 10:03:17PM +0900, Namhyung Kim wrote: > > Currently perf inject just repipes the event without any flush. It > > makes an issue that it changes the order of events processed. > > > > Normally we want to process events in time order, but events are > > recorded from several cpus and they weren't sorted with each other. > > So we put them into the ordered event queue, sorted by time, and flush > > them when we see a next FINISHED_ROUND event. > > > > But this is for events from kernel, user space events (like the > > FINISHED_ROUND) are processed without queueing. So during the perf > > inject, it writes all the FINISHED_ROUND events directly while > > SAMPLE (and other) events are kept in the queue. This makes the user > > space events are put before any kernel events. > > > > You can see that with the following command: > > > > $ perf record -a -o- sleep 1 | perf inject -b | perf script -i- --show-round-events > > PERF_RECORD_FINISHED_ROUND > > PERF_RECORD_FINISHED_ROUND > > PERF_RECORD_FINISHED_ROUND > > ... > > > > Omitting perf inject, you can see the events are placed in the middle > > of the data. > > > > You might argue that the whole point of the FINISHED_ROUND event is to > > sort (kernel) events. And after perf inject, all events are written > > in a proper time order so we don't care about the FINISHED_ROUND event > > anymore. > > > > But the problem is we don't know whether the input data is sorted or > > not (maybe we can add a feature bit for this?) so it should use an > > ordered event queue when processing the input like in perf report. > > I like the idea of storing the information that the data is sorted, > and when it's there, let's not use ordered_oevets
Thanks for your input. Yeah, I think it's better not to use it if possible.
> > > > > Remember all the FINISHED_ROUND events now come before other events so > > the tool cannot know when it can flush the data so everything will be > > queued until it meets the end of the input. Actually it's same for > > perf inject itself as it doesn't flush the queue. > > > > Below measures time and memory usage during the perf inject and > > report using ~190MB data file. > > > > Before: > > perf inject: 11.09 s, 382148 KB > > perf report: 8.05 s, 397440 KB > > > > After: > > perf inject: 16.24 s, 83376 KB > > perf report: 7.96 s, 216184 KB > > > > As you can see, it used 2x memory of the input size. I guess it's > > because it needs to keep the copy for the whole input. But I don't > > understand why processing time of perf inject increased.. > > would be good to find out first
Will do!
Thanks Namhyung
| |