linux-kernel - Re: [REGRESSION][BISECT] perf/core: Remove pmu linear searching code

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Date:   Mon, 5 Jun 2023 15:13:24 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        jolsa@...nel.org, irogers@...gle.com, bp@...en8.de,
        adrian.hunter@...el.com, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [REGRESSION][BISECT] perf/core: Remove pmu linear searching code

On 05-Jun-23 3:04 PM, Peter Zijlstra wrote:
> On Mon, Jun 05, 2023 at 11:27:31AM +0200, Peter Zijlstra wrote:
>> On Mon, Jun 05, 2023 at 08:10:15AM +0100, Mark Rutland wrote:
>>
>>> How does this work on x86? Do you have pseudo-PMUs for PERF_TYPE_HARDWARE and
>>> PERF_TYPE_RAW ?
>>
>> Generic code maps TYPE_HARDWARE and TYPE_HW_CACHE to TYPE_RAW for a
>> first go, only if that fails it will try the actual type.
>>
>> And x86 has the (first) CPU PMU has TYPE_RAW, on hybrid, it will
>> transparently pick the right actual PMU.
> 
> Oh, I might've misread that last bit.. TYPE_RAW is always the big core,
> it will not magic the thing. If you want little events you gotta
> manually find the little pmu.

"manually find the little pmu" ... which was being done by linear searching?

Thanks,
Ravi