linux-kernel - Re: [PATCH V3 0/5] bugs fix for large PEBS mmap read and rdpmc read

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Date:   Wed, 31 Jan 2018 10:15:33 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH V3 0/5] bugs fix for large PEBS mmap read and rdpmc read



On 1/31/2018 8:15 AM, Jiri Olsa wrote:
> On Wed, Jan 31, 2018 at 10:15:39AM +0100, Jiri Olsa wrote:
>> On Tue, Jan 30, 2018 at 07:59:41PM -0800, Andi Kleen wrote:
>>>> Still, the part I am missing here, is why asking for
>>>> PERF_SAMPLE_PERIOD voids large PEBS.
>>>
>>> I think it was disabled together with frequency mode
>>> (which we could support too, but it's a bit more work)
>>>
>>> But yes PERIOD could probably be allowed.
>>
>> looks like it's just a matter of adding PERF_SAMPLE_PERIOD
>> into PEBS_FREERUNNING_FLAGS, we already populate period
>> in setup_pebs_sample_data
>>
>> jirka
>>
>>
>> ---
>> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
>> index 8e4ea143ed96..78f91ec1056e 100644
>> --- a/arch/x86/events/perf_event.h
>> +++ b/arch/x86/events/perf_event.h
>> @@ -93,7 +93,8 @@ struct amd_nb {
>>   	PERF_SAMPLE_ID | PERF_SAMPLE_CPU | PERF_SAMPLE_STREAM_ID | \
>>   	PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | \
>>   	PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR | \
>> -	PERF_SAMPLE_REGS_INTR | PERF_SAMPLE_REGS_USER)
>> +	PERF_SAMPLE_REGS_INTR | PERF_SAMPLE_REGS_USER | \
>> +	PERF_SAMPLE_PERIOD)
> 
> seems to work, getting large PEBS event for following command line:
> 
>    perf record -e cycles:P -c 100 --no-timestamp -C 0 --period
> 
> 

Yes, I tried the patch. The large PEBS can be enabled with the PERIOD 
flag. Everything looks good.

Jirka, could you please post the patch as well?

Thanks,
Kan