linux-kernel - Re: [RFC][PATCH] ring-buffer: Have nested events still record running time stamp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20200629232652.5872c966@oasis.local.home>
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