From: "John Hawkes" <hawkes@sgi.com>
To: linux-ia64@vger.kernel.org
Subject: Re: [PATCH] - sched_clock() broken for ia64 SN platform
Date: Thu, 20 Nov 2003 22:14:36 +0000 [thread overview]
Message-ID: <marc-linux-ia64-106936655210703@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-106928980122896@msgid-missing>
From: "john stultz" <johnstul@us.ibm.com>
> I too was confused why per-cpu start and stop times were not just used
> for this high-res accounting. I'm not sure I can look into it now, but
> I'd be interested to hear why we'd compare timestamps across cpus
> (rather then just use time deltas calculated on a single cpu).
sched_clock() and task->timestamp are used in two different ways. One is for
supposedly high-res accounting. The other is for can_migrate_task(), called
during load-balancing, to determine if the process has slept long enough to
consider it to no longer be cache-hot. It's this latter use that suffers from
a drifty timebase.
John Hawkes
prev parent reply other threads:[~2003-11-20 22:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-20 0:56 [PATCH] - sched_clock() broken for ia64 SN platform John Hawkes
2003-11-20 1:24 ` David Mosberger
2003-11-20 4:09 ` John Hawkes
2003-11-20 6:01 ` David Mosberger
2003-11-20 15:23 ` Jack Steiner
2003-11-20 17:25 ` Grant Grundler
2003-11-20 17:25 ` Rich Altmaier
2003-11-20 18:32 ` David Mosberger
2003-11-20 19:20 ` Robin Holt
2003-11-20 19:23 ` Robin Holt
2003-11-20 20:58 ` John Hawkes
2003-11-20 21:27 ` David Mosberger
2003-11-20 21:58 ` john stultz
2003-11-20 22:14 ` John Hawkes [this message]
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