linux-kernel - Re: [PATCH V4 07/14] perf/x86/intel: Support hardware TopDown metrics

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Date:   Mon, 30 Sep 2019 18:21:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V4 07/14] perf/x86/intel: Support hardware TopDown metrics

On Mon, Sep 30, 2019 at 12:17:57PM -0400, Liang, Kan wrote:
> 
> 
> On 9/30/2019 10:53 AM, Peter Zijlstra wrote:
> > 
> > After that, I think we can simply do something like:
> > 
> > icl_update_topdown_event(..)
> 
> We should call this function in x86_pmu_commit_txn()?

Nah, we could use that TXN_READ stuff, but I don't think we have to. We
just raely on having done all ->read() callbacks before doing
perf_event_count().

> > {
> > 	int idx = event->hwc.idx;
> > 
> > 	if (is_metric_idx(idx))
> > 		return;
> > 
> > 	// must be FIXED_SLOTS
> 
> The FIXED_SLOTS may not be in the group.

Argh.. can we mandate that it is? that is, if you want a metric thing,
you have to have a slots counter first?