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Subject: Re: [PATCH v8 0/8] Don't compute events that won't be used in a
 metric.
To:     Ian Rogers <irogers@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        linux-kernel@vger.kernel.org, Jin Yao <yao.jin@linux.intel.com>,
        John Garry <john.garry@huawei.com>,
        Paul Clarke <pc@us.ibm.com>, kajoljain <kjain@linux.ibm.com>,
        linux-perf-users@vger.kernel.org
Cc:     Stephane Eranian <eranian@google.com>,
        Sandeep Dasgupta <sdasgup@google.com>
References: <20210918063513.2356923-1-irogers@google.com>
From:   Andi Kleen <ak@linux.intel.com>
Message-ID: <7307f6f3-74a8-ef3e-428b-fc294454e463@linux.intel.com>
Date:   Mon, 20 Sep 2021 06:46:14 -0700
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On 9/17/2021 11:35 PM, Ian Rogers wrote:
>      
> For a metric like:
>    EVENT1 if #smt_on else EVENT2
>      
> currently EVENT1 and EVENT2 will be measured and then when the metric
> is reported EVENT1 or EVENT2 will be printed depending on the value
> from smt_on() during the expr parsing. Computing both events is
> unnecessary and can lead to multiplexing as discussed in this thread:
> https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/
>
> This change modifies expression parsing so that constants are
> considered when building the set of ids (events) and only events not
> contributing to a constant value are measured.


The series looks good to me.


Reviewed-by: Andi Kleen <ak@linux.intel.com>


-Andi