Messages in this thread | | | Date | Thu, 25 Nov 2021 20:30:53 +0800 | From | Leo Yan <> | Subject | Re: [RESEND PATCH 1/1] perf arm-spe: report all SPE records as "all" events |
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On Thu, Nov 25, 2021 at 10:21:48AM +0000, James Clark wrote: > On 25/11/2021 07:53, Leo Yan wrote:
[...]
> >> +static int arm_spe__synth_other_sample(struct arm_spe_queue *speq, > >> + u64 spe_events_id) > >> +{ > >> + struct arm_spe *spe = speq->spe; > >> + struct arm_spe_record *record = &speq->decoder->record; > >> + union perf_event *event = speq->event_buf; > >> + struct perf_sample sample = { .ip = 0, }; > >> + > >> + arm_spe_prep_sample(spe, speq, event, &sample); > >> + > >> + sample.id = spe_events_id; > >> + sample.stream_id = spe_events_id; > >> + sample.addr = record->to_ip; > > > > After checked the event types, I think "other" samples would include > > below raw event types: > > Maybe we should rename some of the functions and variables if there is > confusion, but I think this new group is "all" rather than "other" because > it also includes all the events that would be put in other groups. > > > > > EV_EXCEPTION_GEN > > EV_RETIRED > > EV_NOT_TAKEN > > EV_ALIGNMENT > > EV_PARTIAL_PREDICATE > > EV_EMPTY_PREDICATE > > > > I am just wander if we can use sample.transaction to store these event > > types, otherwise, we cannot distinguish the event type for the samples. > > If we can use the transaction field to distinguish sample types, I'm > wondering why we need the separate groups at all. If this new group > includes all sample types, and they're all labelled, do we need to > continue with the other groups like "tlb-access" and "branch-miss"?
I admit the samples for "tlb-access" and "branch-miss" might not a good practice. At the time when I was upstreaming the Arm SPE patches (mainly based Hisilicon patches), the main idea for use some events to output samples, this is why "tlb-access" and "branch-miss" events were introduced.
But when worked on Arm SPE for enabling "perf mem" and "perf c2c", I recognized that _consuming_ hardware trace data is much more important than merely outputting samples. A better way for _consuming_ the Arm SPE trace data is to synthesize samples with a prominent type and use an extra field in sample for the associated attribution. E.g. we can synthesize memory samples and uses field "sample.data_src" to distinguish different memory attributions, thus the events "tlb-access" and "branch-miss" are not useful. This approach can be applied to instruction event and branch event, and both of them use field "sample.flags" to indicate what's the type of instruction or branch.
If we follow up this approach, below records can be considered to synthesize instruction or branch samples:
EV_EXCEPTION_GEN EV_RETIRED EV_NOT_TAKEN
Below records can be considered to generate memory samples:
EV_ALIGNMENT EV_PARTIAL_PREDICATE EV_EMPTY_PREDICATE
We can consider to extend sample's three fields: sample::flags for instruction/branch samples sample::data_srouce for memory samples sample::transaction for memory transactions (see macros with prefix PERF_TXN_).
> Or does the perf GUI not allow filtering by transaction type?
To be honest, when introduced the events "tlb-access" and "branch-miss", I didn't consider transaction type at all.
Thanks, Leo
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