From: Ingo Molnar <mingo@kernel.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: John Stultz <john.stultz@linaro.org>,
Feng Tang <feng.tang@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: Fwd: [GIT PULL] timer changes for v3.10
Date: Wed, 8 May 2013 08:44:19 +0200 [thread overview]
Message-ID: <20130508064419.GA5378@gmail.com> (raw)
In-Reply-To: <20130507215151.GB10061@amd.pavel.ucw.cz>
* Pavel Machek <pavel@ucw.cz> wrote:
> > Sorry. You seem to not like the merged change, but I guess I'm not
> > quite sure what exactly your objection is here.
>
> I'm not exactly sure what my objections are.
>
> TSC was not designed for long-term precise timekeeping. [...]
The TSC is just a 64-bit counter that can be read very cheaply.
If the TSC is _implemented_ precisely in hardware and is kept in sync over
CPUs then it's obviously fit for long-term precise timekeeping from that
point on.
> [...] I guess it may work ok for short naps, [...]
Historically the TSC was not very precise nor kept in sync, but see the
measurements from Feng Tang, it's very precise now on good hardware - and
it's also a very cheap to read clocksource.
> [...] but some people suspend their machines for longer than that. Plus
> I wonder how it will interfere with /etc/adjtime.
If it's precise then why should it interfere?
The history of the TSC being problematic can be ignored the moment CPU
makers fix it completely - and apparently that is happening...
Thanks,
Ingo
next prev parent reply other threads:[~2013-05-08 6:44 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-30 7:43 [GIT PULL] timer changes for v3.10 Ingo Molnar
2013-04-30 15:21 ` Linus Torvalds
2013-05-01 10:53 ` Ingo Molnar
2013-05-02 10:22 ` Thomas Gleixner
2013-05-06 23:01 ` Pavel Machek
2013-05-07 0:10 ` John Stultz
[not found] ` <CA++bM2scosWgBpC3_LzcKYOjG4EQQzN5Vf4rZFds-5qRVRwvDQ@mail.gmail.com>
2013-05-07 2:38 ` Fwd: " Feng Tang
2013-05-07 6:53 ` Ingo Molnar
2013-05-07 7:05 ` Feng Tang
2013-05-07 16:01 ` John Stultz
2013-05-07 17:18 ` Ingo Molnar
2013-05-07 21:31 ` Pavel Machek
2013-05-07 21:39 ` John Stultz
2013-05-07 21:51 ` Pavel Machek
2013-05-08 6:44 ` Ingo Molnar [this message]
2013-05-08 10:55 ` Pavel Machek
2013-05-08 14:11 ` Feng Tang
2013-05-08 14:34 ` Thomas Gleixner
2013-05-08 19:49 ` Pavel Machek
2013-05-09 8:59 ` Ingo Molnar
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