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Date: Mon, 29 Jun 2020 23:26:52 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com> Cc: linux-kernel <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Masami Hiramatsu <mhiramat@...nel.org>, Arnaldo Carvalho de Melo <acme@...hat.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Yordan Karadzhov <y.karadz@...il.com>, Tzvetomir Stoyanov <tz.stoyanov@...il.com>, Tom Zanussi <zanussi@...nel.org>, Jason Behmer <jbehmer@...gle.com>, Julia Lawall <julia.lawall@...ia.fr>, Clark Williams <williams@...hat.com>, bristot <bristot@...hat.com>, Daniel Wagner <wagi@...om.org>, Darren Hart <dvhart@...are.com>, Jonathan Corbet <corbet@....net>, "Suresh E. Warrier" <warrier@...ux.vnet.ibm.com>, "Joel Fernandes, Google" <joel@...lfernandes.org> Subject: Re: [RFC][PATCH] ring-buffer: Have nested events still record running time stamp On Mon, 29 Jun 2020 23:13:32 -0400 (EDT) Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote: > -> This configuration's avg varies between 239 and 256 ns based on your benchmark methodology. The std. dev. varies between > 138 and 201 ns. > > In the benchmark results you collected, config #1 appeared to have little delta between xadd and cmpxchg, whereas > config #2 and #3 had some avg difference. Did you try running this test many times on each machine to see if the > result was indeed stable ? Yes, but as we discussed on IRC, my machines are much smaller than this one, and that makes it a bit more deterministic. I also run them with distro configs. When there's debugging enabled, I get much more erratic results. -- Steve
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