linux-kernel - Re: [PATCH 0/2] perf/x86: Add ability to sample TSC

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

Message-ID: <CALAqxLVDfGhim1+iO=_mXmrpc6vWGmjFJGCRBx39rM0RXobr+Q@mail.gmail.com>
Date:	Thu, 19 Feb 2015 09:24:17 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Pawel Moll <pawel.moll@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 0/2] perf/x86: Add ability to sample TSC

On Thu, Feb 19, 2015 at 4:11 AM, Adrian Hunter <adrian.hunter@...el.com> wrote:
> Hi
>
> With the advent of switching perf_clock to CLOCK_MONOTONIC,
> it will not be possible to convert perf_clock directly to/from
> TSC. So add the ability to sample TSC instead.
>
>
> Adrian Hunter (2):
>       perf: Sample additional clock value
>       perf/x86: Provide TSC for PERF_SAMPLE_CLOCK_ARCH

This doesn't seem very portable. The CLOCK_MONOTONIC_RAW clockid was
added to provide a arch-neutral abstraction of a free-running hardware
counter that isn't affected by adjtimex slewing (though like any
counter, it will be affected by non-constant drift).

You might consider looking at that if the short term slew adjustments
(which result in more accurate timings in the long term) are
problematic for you.

thanks
-john
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/