On Fri, Sep 14, 2018 at 02:13:07PM +0200, Ingo Molnar wrote: > > * Peter Zijlstra <pet...@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?
yep.. fair amount ;-) wasn't that bad in my tests, but could be evil on some really big server > > 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. ok, separate files it is jirka
