From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Karsten Wiese <fzu@wemgehoertderstaat.de>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: set_cyc2ns_scale() remove tsc_now and ns_now
Date: Fri, 11 Apr 2008 09:55:54 +0200 [thread overview]
Message-ID: <20080411075554.GA6834@elte.hu> (raw)
In-Reply-To: <873apsn8g7.fsf@basil.nowhere.org>
* Andi Kleen <andi@firstfloor.org> wrote:
> (actually it is still the wrong time -- really needs a grace period
> during which the TSC is not used
> ftp://firstfloor.org/pub/ak/quilt/patches/sched-clock implemented some
> of these ideas against an older kernel)
recent CPUs have constant-freq TSCs so it's mostly a legacy issue, but
the affected installed base is still significant to warrant a fix.
we dont really have to worry about complications like grace periods -
higher layers in the scheduler protect against temporary sched_clock()
outliers. So i think this can all be done much simpler. Just get rid of
the global cpu_khz notion, sched_clock() should simply follow the ->freq
value - and that's it.
Ingo
next prev parent reply other threads:[~2008-04-11 7:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-10 21:31 [PATCH] x86: set_cyc2ns_scale() remove tsc_now and ns_now Karsten Wiese
2008-04-11 7:42 ` Andi Kleen
2008-04-11 7:55 ` Ingo Molnar [this message]
2008-04-11 8:06 ` Andi Kleen
2008-04-11 8:25 ` Guillaume Chazarain
2008-04-11 8:40 ` Andi Kleen
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