linux-kernel - Re: [PATCH] perf/x86/intel/ds: fix precise store latency handling

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Message-ID: <Yv36DrUKLz8UWnbX@worktop.programming.kicks-ass.net>
Date:   Thu, 18 Aug 2022 10:36:30 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kan.liang@...el.com,
        ak@...ux.intel.com, acme@...hat.com, namhyung@...nel.org,
        irogers@...gle.com
Subject: Re: [PATCH] perf/x86/intel/ds: fix precise store latency handling

On Wed, Aug 17, 2022 at 10:46:13PM -0700, Stephane Eranian wrote:
> With the existing code in store_latency_data(), the memory operation (mem_op)
> returned to the user is always OP_LOAD where in fact, it should be OP_STORE.
> This comes from the fact that the function is simply grabbing the information
> from a data source map which covers only load accesses. Intel 12th gen CPU
> offers precise store sampling that captures both the data source and latency.
> Therefore it can use the data source mapping table but must override the
> memory operation to reflect stores instead of loads.
> 
> Fixes: 61b985e3e775 ("perf/x86/intel: Add perf core PMU support for Sapphire Rapids")
> Signed-off-by: Stephane Eranian <eranian@...gle.com>

Thanks