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(a)dachary.org
<mailto:loic@dachary.org>> 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/2…
<https://www.drdobbs.com/parallel/understanding-and-avoiding-memory-issues/212400410>
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--
Loïc Dachary, Artisan Logiciel Libre
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