linux-kernel - Re: [PATCH v2]: fix Haswell precise store data source encoding

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Message-ID: <CABPqkBQtF_ojuDKXAE+WtJ8x7n6QbQOPwFGWJFXSo==oHv3nWQ@mail.gmail.com>
Date:	Thu, 15 May 2014 22:08:51 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jiri Olsa <jolsa@...hat.com>, Joe Mario <jmario@...hat.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: Re: [PATCH v2]: fix Haswell precise store data source encoding

On Thu, May 15, 2014 at 9:56 PM, Don Zickus <dzickus@...hat.com> wrote:
> On Thu, May 15, 2014 at 05:56:44PM +0200, Stephane Eranian wrote:
>>
>> This patch fixes a bug in  precise_store_data_hsw() whereby
>> it would set the data source memory level to the wrong value.
>>
>> As per the the SDM Vol 3b Table 18-41 (Layout of Data Linear
>> Address Information in PEBS Record), when status bit 0 is set
>> this is a L1 hit, otherwise this is a L1 miss.
>>
>> This patch encodes the memory level according to the specification.
>>
>> In V2, we added the filtering on the store events.
>> Only the following events produce L1 information:
>>  * MEM_UOPS_RETIRED.STLB_MISS_STORES
>>  * MEM_UOPS_RETIRED.LOCK_STORES
>>  * MEM_UOPS_RETIRED.SPLIT_STORES
>>  * MEM_UOPS_RETIRED.ALL_STORES
>
> This worked great on our Haswell-EX box.  I was a little surprised to find
> out it did until I realized on Ivy Bridge 'mem-store' was a 0x02cd but on
> Haswell it is now a 0x82d0.  Go generic event types! :-)
>
> Looking at the SDM documentation it does say something about
> 'UOPS_RETIRED.ALL' supporting stores too but can't find that event.  Is
> that a typo, much like the 0x02 umask for stores on the D0 event is
> missing from the documentation?  Just wanted to make sure we are not
> missing one more case.
>
But uops_retired.all does not generate the L1 info. That is why it is not
there in my patch.

> Thanks for the quick patch Stephane!
>
> Tested-and-Reviewed-by: Don Zickus <dzickus@...hat.com>
>
>>
>> Signed-off-by: Stephane Eranian <eranian@...gle.com>
>>
>> diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
>> index ae96cfa..980970c 100644
>> --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
>> +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
>> @@ -108,15 +108,31 @@ static u64 precise_store_data(u64 status)
>>       return val;
>>  }
>>
>> -static u64 precise_store_data_hsw(u64 status)
>> +static u64 precise_store_data_hsw(struct perf_event *event, u64 status)
>>  {
>>       union perf_mem_data_src dse;
>> +     u64 cfg = event->hw.config & INTEL_ARCH_EVENT_MASK;
>>
>>       dse.val = 0;
>>       dse.mem_op = PERF_MEM_OP_STORE;
>>       dse.mem_lvl = PERF_MEM_LVL_NA;
>> +
>> +     /*
>> +      * L1 info only valid for following events:
>> +      *
>> +      * MEM_UOPS_RETIRED.STLB_MISS_STORES
>> +      * MEM_UOPS_RETIRED.LOCK_STORES
>> +      * MEM_UOPS_RETIRED.SPLIT_STORES
>> +      * MEM_UOPS_RETIRED.ALL_STORES
>> +      */
>> +     if (cfg != 0x12d0 && cfg != 0x22d0 && cfg != 0x42d0 && cfg != 0x82d0)
>> +             return dse.mem_lvl;
>> +
>>       if (status & 1)
>> -             dse.mem_lvl = PERF_MEM_LVL_L1;
>> +             dse.mem_lvl = PERF_MEM_LVL_L1 | PERF_MEM_LVL_HIT;
>> +     else
>> +             dse.mem_lvl = PERF_MEM_LVL_L1 | PERF_MEM_LVL_MISS;
>> +
>>       /* Nothing else supported. Sorry. */
>>       return dse.val;
>>  }
>> @@ -887,7 +903,7 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
>>                               data.data_src.val = load_latency_data(pebs->dse);
>>                       else if (event->hw.flags & PERF_X86_EVENT_PEBS_ST_HSW)
>>                               data.data_src.val =
>> -                                     precise_store_data_hsw(pebs->dse);
>> +                                     precise_store_data_hsw(event, pebs->dse);
>>                       else
>>                               data.data_src.val = precise_store_data(pebs->dse);
>>               }
--
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