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Date:   Wed, 24 Aug 2022 09:27:05 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ravi Bangoria <ravi.bangoria@amd.com>
Cc:     acme@kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, namhyung@kernel.org, songliubraving@fb.com,
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        ak@linux.intel.com, mark.rutland@arm.com, megha.dey@intel.com,
        frederic@kernel.org, maddy@linux.ibm.com, irogers@google.com,
        kim.phillips@amd.com, linux-kernel@vger.kernel.org,
        santosh.shukla@amd.com
Subject: Re: [RFC v2] perf: Rewrite core context handling
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On Wed, Aug 24, 2022 at 10:37:36AM +0530, Ravi Bangoria wrote:

> > Now, I suppose making that:
> > 
> >   {-1, NULL, NULL}, {cpu, NULL, NULL}
> > 
> > could work, but wouldn't iterating the the tree be more expensive than
> > just finding the sub-trees as we do now?
> 
> pmu=NULL can be used while scheduling entire context. We can just traverse
> through all pmu events of both cpu subtrees.

But imagine the case where we have 50 event for a PMU that can only
schedule 8. Then we have to iterate 42 events for naught instead of
directly jumping to the next PMU.