Messages in this thread | | | Date | Fri, 14 Sep 2018 14:13:07 +0200 | From | Ingo Molnar <> | Subject | Re: [RFCv2 00/48] perf tools: Add threads to record command |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Sep 14, 2018 at 01:47:25PM +0200, Jiri Olsa wrote: > > On Fri, Sep 14, 2018 at 01:15:28PM +0200, Peter Zijlstra wrote: > > > On Fri, Sep 14, 2018 at 11:40:22AM +0200, Ingo Molnar wrote: > > > > In fact keeping the files separate has scalability advantages for 'perf report' and similar > > > > parsing tools: they could read all the streams in a per-CPU fashion already, from the very > > > > beginning. > > > > > > Also writing to different files from different CPUs is good for record, > > > less contention on the inode state (which include pagecache). > > > > maybe I should explain a little bit more on this > > > > we write to different (per-cpu) files during the record, > > and at the end of the session, we take them and store > > them inside perf.data > > How long does it take to combine that? If we generated a lot of data, > that could take a fair amount of time, no? > > I feel that record should not mysteriously 'hang' when it is done. It > used to do that at some point because of that stupid .debug crap, but > acme fixed that I think.
Agreed - plus at the report stage it would be advantageous to be able to *read* per-cpu files as well.
If we do things smartly them report will create similar NUMA affinity as the record session used.
Thanks,
Ingo
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