linux-kernel - Re: [PATCH V4 04/23] perf/x86/intel: Support adaptive PEBSv4

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Date:   Wed, 27 Mar 2019 07:42:22 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     peterz@...radead.org, 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
Subject: Re: [PATCH V4 04/23] perf/x86/intel: Support adaptive PEBSv4

> We need to call perf_event_overflow() for the last record of each event.
> It's hard to detect which record is the last record of the event with one
> pass walking.
> 
> Also, I'm not sure how much we can save with one pass walking. The
> optimization should only benefit large PEBS. The total number of records for
> large PEBS should not be huge.
> I will evaluate the performance impact of one pass walking. If there is
> observed performance improvement, I will submit a separate patch later.
> 
> For now, I think we can still use the mature two pass walking method.

Okay sounds reasonable to keep it then.

Thanks,

-Andi