linux-kernel - Re: [PATCH V6 03/16] perf/core: Add support for PERF_SAMPLE_CODE_PAGE

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Date:   Mon, 10 Aug 2020 18:37:08 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, eranian@...gle.com, ak@...ux.intel.com,
        dave.hansen@...el.com, kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH V6 03/16] perf/core: Add support for
 PERF_SAMPLE_CODE_PAGE_SIZE



On 8/10/2020 5:41 PM, Peter Zijlstra wrote:
> On Mon, Aug 10, 2020 at 02:24:23PM -0700, Kan Liang wrote:
>> From: Stephane Eranian <eranian@...gle.com>
>>
>> When studying code layout, it is useful to capture the page size of the
>> sampled code address.
>>
>> Add a new sample type for code page size.
>> The new sample type requires collecting the ip. The code page size can
>> be calculated from the IRQ-safe perf_get_page_size().
>>
>> Only the generic support is covered. The large PEBS will be disabled
>> with this sample type.
> 
> -ENOREASON

I think the reason is similar to PERF_SAMPLE_DATA_PAGE_SIZE. For large 
PEBS, the mapping could be gone for the earlier PEBS records. Invalid 
page size may be retrieved. I will update the commit message.

Thanks,
Kan