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Date:   Wed, 24 Aug 2022 13:23:28 +0530
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Subject: Re: [RFC v2] perf: Rewrite core context handling
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To:     Peter Zijlstra <peterz@infradead.org>
Cc:     acme@kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, namhyung@kernel.org, songliubraving@fb.com,
        eranian@google.com, alexey.budankov@linux.intel.com,
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        frederic@kernel.org, maddy@linux.ibm.com, irogers@google.com,
        kim.phillips@amd.com, linux-kernel@vger.kernel.org,
        santosh.shukla@amd.com, ravi.bangoria@amd.com
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From:   Ravi Bangoria <ravi.bangoria@amd.com>
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On 24-Aug-22 12:57 PM, Peter Zijlstra wrote:
> 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.

Yes, that needs to be handled. And, IIRC, you proposed maintaining a list
of leftmost event from each pmu subtree.

Thanks,
Ravi