Messages in this thread | | | Date | Mon, 21 Nov 2022 11:55:17 +0000 | Subject | Re: [PATCH RFC 0/6] Add metrics for neoverse-n2 | From | James Clark <> |
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On 19/11/2022 21:46, Ian Rogers wrote: > On Fri, Nov 18, 2022 at 7:30 PM Jing Zhang <renyu.zj@linux.alibaba.com> > wrote: >> >> >> 在 2022/11/16 下午7:19, James Clark 写道: >>> >>> >>> On 31/10/2022 11:11, Jing Zhang wrote: >>>> This series add six metricgroups for neoverse-n2, among which, the >>>> formula of topdown L1 is from the document: >>>> > https://documentation-service.arm.com/static/60250c7395978b529036da86?token= >>>> >>>> Since neoverse-n2 does not yet support topdown L2, metricgroups such >>>> as Cache, TLB, Branch, InstructionsMix, and PEutilization are added to >>>> help further analysis of performance bottlenecks. >>>> >>> >>> Hi Jing, >>> >>> Thanks for working on this, these metrics look ok to me in general, >>> although we're currently working on publishing standardised metrics >>> across all new cores as part of a new project in Arm. This will include >>> N2, and our ones are very similar (or almost identical) to yours, >>> barring slightly different group names, metric names, and differences in >>> things like outputting topdown metrics as percentages. >>> >>> We plan to publish our standard metrics some time in the next 2 months. >>> Would you consider holding off on merging this change so that we have >>> consistant group names and units going forward? Otherwise N2 would be >>> the odd one out. I will send you the metrics when they are ready, and we >>> will have a script to generate perf jsons from them, so you can review. >>> >>> We also have a slightly different forumula for one of the top down >>> metrics which I think would be slightly more accurate. We don't have >>> anything for your "PE utilization" metrics, which I can raise >>> internally. It could always be added to perf on top of the standardised >>> ones if we don't add it to our standard ones. >>> >>> Thanks >>> James >>> >> >> Hi James, >> >> Regarding the arm n2 standard metrics last time, is my understanding > correct, >> and does it meet your meaning? If so, may I ask when you will send me the >> standards you formulate so that I can align with you in time over my > patchset. >> Please communicate this matter so that we can understand each other's > schedule. >> >> Thanks, >> Jing > > Hi, > > In past versions of the perf tool the metrics have been pretty broken. If > we have something that is good we shouldn't be holding it to a bar of being > perfect, we can merge what we have and improve over time. In this case what > Jing has prepared may arrive in time for Linux 6.2 whilst the standard > metrics may arrive in time for 6.3. I'd suggest merging Jing's work and > then improving on it with the standard metrics. >
I'm not completely opposed to this, I was just worried about the churn because ours will be generated from a script, and that it would end up looking like a mass replacement of these that would have only recently been added.
But maybe that's fine like you say.
> In terms of the metrics themselves, could we add ScaleUnit? For example: > > + { > + "MetricExpr": "LD_SPEC / INST_SPEC", > + "PublicDescription": "The rate of load instructions speculatively > executed to overall instructions speclatively executed", > + "BriefDescription": "The rate of load instructions speculatively > executed to overall instructions speclatively executed", > + "MetricGroup": "InstructionMix", > + "MetricName": "load_spec_rate" > + }, > > A ScaleUnit of "100%" would likely make things more readable. > > Thanks, > Ian >
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