From: Andi Kleen <ak@suse.de>
To: Ray Bryant <raybry@mpdtxmail.amd.com>
Cc: Daniel Jacobowitz <dan@debian.org>,
john stultz <johnstul@us.ibm.com>, Andi Kleen <ak@suse.de>,
Andrew Morton <akpm@osdl.org>,
lkml <linux-kernel@vger.kernel.org>,
discuss@x86-64.org
Subject: Re: [discuss] Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs
Date: Wed, 21 Sep 2005 17:04:04 +0200 [thread overview]
Message-ID: <20050921150404.GD12810@verdi.suse.de> (raw)
In-Reply-To: <200509211015.09356.raybry@mpdtxmail.amd.com>
On Wed, Sep 21, 2005 at 10:15:08AM -0500, Ray Bryant wrote:
> On Tuesday 20 September 2005 23:03, Daniel Jacobowitz wrote:
>
> >
> > FYI, at least I have reproduced this without powernow loaded.
>
> There are cases that we are aware of where the TSC will count slower while the
> processor is halted. This can make TSC's get out of sync on dual cores.
Ok thanks for the confirmation. I guess John's patch is ok then.
Drawback is much slower to extremly slow gettimeofday (depending
if the chipset/BIOS has usable HPET, most seem not to)
>
> I wonder if you can reproduce this problem while also running a pair of cpu
> bound tasks on your dual core box. If you can't, then this is the culprit.
>
> In general, however, on multisocket systems, you can't depend on TSC's being
> synchronized between sockets, so all of this is moot. We just have to deal
> with it.
We handle this, but single socket dual core was special cased because
I was told previously it should be ok.
-Andi
next prev parent reply other threads:[~2005-09-21 15:04 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-19 19:16 [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs john stultz
2005-09-19 19:31 ` Andi Kleen
2005-09-19 19:42 ` john stultz
2005-09-19 19:49 ` [discuss] " Andi Kleen
2005-09-20 18:59 ` john stultz
2005-09-21 4:03 ` Daniel Jacobowitz
2005-09-21 15:15 ` Ray Bryant
2005-09-21 15:04 ` Andi Kleen [this message]
2005-09-21 15:46 ` Ray Bryant
2005-09-22 8:00 ` Jonas Oreland
2005-09-21 20:17 ` Andrew Morton
2005-10-07 12:26 ` Vladimir B. Savkin
2005-10-07 12:31 ` Andi Kleen
2005-10-07 14:15 ` Vladimir B. Savkin
2005-10-07 14:21 ` [discuss] " Velu Erwan
2005-10-08 10:11 ` Vladimir B. Savkin
2005-10-10 18:03 ` john stultz
2005-10-10 18:12 ` Vladimir B. Savkin
2005-10-10 18:19 ` Jonas Oreland
2005-10-11 7:35 ` Vladimir B. Savkin
2005-10-11 8:06 ` Andi Kleen
2005-10-11 16:27 ` Jonas Oreland
2005-10-25 7:35 ` x86-64: Syncing dualcore cpus TSCs Jonas Oreland
2005-10-25 7:42 ` Andi Kleen
2005-10-26 0:05 ` David Lang
-- strict thread matches above, loose matches on Subject: below --
2005-09-20 19:13 [discuss] Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs Langsdorf, Mark
2005-09-20 19:24 ` Scott Lampert
2005-09-20 19:30 ` john stultz
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