Messages in this thread | | | Date | Wed, 18 May 2022 14:12:21 +0800 | From | Leo Yan <> | Subject | Re: [PATCH v2 9/11] perf c2c: Sort on peer snooping for load operations |
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Hi Adam,
On Fri, May 13, 2022 at 05:05:45PM +0800, Adam Li wrote:
[...]
> > As result, we can get the 'peer' display as below: > > > > # perf c2c report -d peer --coalesce tid,pid,iaddr,dso -N --stdio > > > > Hi Leo, > > I tested v2 patch on 2P Altra system. > In case the false-sharing data is mainly from remote node, 'Snoop Peers' > cannot indicate severity of false-sharing. As showed in bellow output, > there are only 10 'Load HIT Peer' records, while there are 2353 > 'Load Remote DRAM' records. > > And the name 'Load Remote DRAM' is kind of misleading, since we cannot tell > the data source is 'DRAM'.
Appreicate for the testing, and your feedback is very helpful.
After some discussion, in the patch set v9 "perf: arm-spe: Decode SPE source and use for perf c2c" (please ignore the typo "v8", actually it's patch set v9), Ali has updated the memory tag setting for the type ARM_SPE_NV_REMOTE. I think the prominent change is we set PERF_MEM_SNOOPX_PEER flag for remote access.
Please note, in the total statistics, all remote accesses will be accounted into metric "rmt_hit", so "rmt_hit" includes the access for remote DRAM or any upwards cache levels due we cannot distinguish them.
From my experiment, with this updating the output result is promised for the peer accesses and it's easier for inspecting false sharing.
As you might see I have prepared a git repo: https://git.linaro.org/people/leo.yan/linux-spe.git/ branch: perf_c2c_arm_spe_peer_v3, which contains the updated patches for both memory flag setting and perf c2c related patches.
Could you confirm if the updated code works for you or not?
Thanks, Leo
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