Messages in this thread | | | Date | Thu, 17 Sep 2020 21:08:54 +0800 | From | Leo Yan <> | Subject | Re: [PATCHv3] perf kvm: add kvm-stat for arm64 |
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Hi Sergey,
On Thu, Sep 17, 2020 at 08:00:28PM +0900, Sergey Senozhatsky wrote: > On (20/09/17 11:21), Marc Zyngier wrote: > > > > On Arm64, ftrace tracepoint "kvm_entry" doesn't contain the field "id" > > > > or field "vcpu_id", thus it always reads out the "id" is 0 and it is > > Right, Leo, I saw that. I put "id", because there is ... well, there is > nothing we can put there. The trace points on arm64, unlike on s390 or x86, > don't contain info which can let us map trace-event to vcpu_id (even > (void *)vcpu would have been rather helpful). > > > > > Essentially, this issue is caused by different archs using different > > > > format for ftrace event "kvm_entry", on x86 it contains feild > > > > "vcpu_id" but arm64 only just records "vcpu_pc". > > Exactly. I wish trace-points were less of pain-points. > > So 'perf kvm stat' on arm64 works, but it's not as feature rich as on other > platforms; at the same it's better than nothing, I suppose.
Agree and I don't want to introduce complexity at here. So it's fine for me to merge your patch v4 firstly and later use a new patch set to support "vcpu_id".
As you might have seen the discussion with Marc for new trace events with "vcpu_id", another way is to add new trace events with "vcpu_id" and then enable "perf kvm stat" based on new trace events.
Either way is okay for me; except maintainers have different thinking for this.
Thanks, Leo
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