Hi Adam, Thanks for the pointer: very informative indeed :-) perf c2c seems to be a good tool and works on my laptop. I'll have to dig deeper to figure out what it does exactly. To be continued! Cheers On 17/03/2021 08:48, Adam Kupczyk wrote: > Loic, > > Here is some discussion on cache false sharing that you may find valuable: https://github.com/ceph/ceph/pull/9431 <https://github.com/ceph/ceph/pull/9431> . > Maybe it is possible to turn perf c2c into some systemic check? > > Best regards, > Adam > > On Tue, 16 Mar 2021 at 22:59, Loïc Dachary <loic@xxxxxxxxxxx <mailto:loic@xxxxxxxxxxx>> wrote: > > > > On 16/03/2021 22:01, Mark Nelson wrote: > > Hi Loïc, > > > > > > I don't have any tests specifically for this, but looking at #39057, I wonder if something could be crafted using the check_shard_select test that Adam wrote as a template. What do you think? > That sounds like a good idea. And maybe using cachegrind[0] also? > > [0] https://www.valgrind.org/docs/manual/cg-manual.html <https://www.valgrind.org/docs/manual/cg-manual.html> > > > > > > Mark > > > > > > On 3/16/21 3:52 PM, Loïc Dachary wrote: > >> Hi Mark, > >> > >> While trying to figure out a random failure in the mempool tests[0] introduced when fixing a bug in how mempool selects shards holding the byte count of a given pool[1] earlier this year, I was intrigued by this "cache line ping pong" problem[2]. And I wonder if you have some kind of benchmark, somewhere in your toolbox, that someone could use to demonstrate the problem. Maybe such a code could be adapted to show the benefit of the optimization implemented in mempool? > >> > >> Cheers > >> > >> [0] https://tracker.ceph.com/issues/49781#note-9 <https://tracker.ceph.com/issues/49781#note-9> > >> [1] https://github.com/ceph/ceph/pull/39057/files <https://github.com/ceph/ceph/pull/39057/files> > >> [2] https://www.drdobbs.com/parallel/understanding-and-avoiding-memory-issues/212400410 <https://www.drdobbs.com/parallel/understanding-and-avoiding-memory-issues/212400410> > >> > >> > >> _______________________________________________ > >> Dev mailing list -- dev@xxxxxxx <mailto:dev@xxxxxxx> > >> To unsubscribe send an email to dev-leave@xxxxxxx <mailto:dev-leave@xxxxxxx> > > _______________________________________________ > > Dev mailing list -- dev@xxxxxxx <mailto:dev@xxxxxxx> > > To unsubscribe send an email to dev-leave@xxxxxxx <mailto:dev-leave@xxxxxxx> > > -- > Loïc Dachary, Artisan Logiciel Libre > > > _______________________________________________ > Dev mailing list -- dev@xxxxxxx <mailto:dev@xxxxxxx> > To unsubscribe send an email to dev-leave@xxxxxxx <mailto:dev-leave@xxxxxxx> > > > _______________________________________________ > Dev mailing list -- dev@xxxxxxx > To unsubscribe send an email to dev-leave@xxxxxxx -- Loïc Dachary, Artisan Logiciel Libre
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