From: Rob Herring <firstname.lastname@example.org> To: "email@example.com" <firstname.lastname@example.org> Cc: "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org> Subject: Re: [PATCH 1/3] libperf: Add processing to scale the counters obtained during the read() system call when multiplexing Date: Tue, 31 Aug 2021 07:26:18 -0500 [thread overview] Message-ID: <CAL_JsqLKD0DZT63MQ9vTumOf1bfRrU9Bt9Qa_GTb1siRsK+Zemail@example.com> (raw) In-Reply-To: <OSBPR01MB4600288E176A169C07BF543EF7C59@OSBPR01MB4600.jpnprd01.prod.outlook.com> On Tue, Aug 24, 2021 at 5:12 AM firstname.lastname@example.org <email@example.com> wrote: > > Hi, Rob > > > On Fri, Aug 20, 2021 at 06:39:06PM +0900, Shunsuke Nakamura wrote: > > > perf_evsel__read() scales counters obtained by RDPMC during multiplexing, but > > > does not scale counters obtained by read() system call. > > > > > > Add processing to perf_evsel__read() to scale the counters obtained during the > > > read() system call when multiplexing. > > > > Which one is right though? Changing what read() returns could break > > users, right? Or are you implying that the RDPMC path is correct and > > read() was not. More likely the former case since I wrote the latter. > > perf_evsel__read() returns both the count obtained by RDPMC and the count obtained > by the read() system call when multiplexed with RDPMC enabled. > > That is, there is a mix of scaled and unscaled values. > > As Rob says, when this patch is applied, rescaling the count obtained from > perf_evsel__read() during multiplexing will break the count. > > I think the easiest solution is to change the value you get from RDPMC to not scale > and let the user scale it, but I thought it would be a little inconvenient. Agreed, unless someone else has an opinion. It would be good to do the scaling in libperf with the optimized math op, but I assume there's some reason the user may need unscaled values? Rob
next prev parent reply other threads:[~2021-08-31 12:26 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-20 9:39 [PATCH 0/3] libperf: Add support for scaling counters obtained from the read() system call during multiplexing Shunsuke Nakamura 2021-08-20 9:39 ` [PATCH 1/3] libperf: Add processing to scale the counters obtained during the read() system call when multiplexing Shunsuke Nakamura 2021-08-23 20:12 ` Rob Herring 2021-08-24 10:11 ` nakamura.shun 2021-08-31 8:58 ` nakamura.shun 2021-08-31 12:26 ` Rob Herring [this message] 2021-09-07 23:59 ` Ian Rogers 2021-09-17 8:04 ` nakamura.shun 2021-08-20 9:39 ` [PATCH 2/3] libperf tests: Fix verbose printing Shunsuke Nakamura 2021-08-23 20:26 ` Rob Herring 2021-08-24 18:06 ` Arnaldo Carvalho de Melo 2021-08-20 9:39 ` [PATCH 3/3] libperf tests: Add test_stat_multiplexing test Shunsuke Nakamura
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