From: Con Kolivas <kernel@kolivas.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>,
Chen@bhhdoa.org.au, Kenneth W <kenneth.w.chen@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: bug in sched.c:activate_task()
Date: Tue, 05 Oct 2004 14:45:49 +1000 [thread overview]
Message-ID: <cone.1096951549.783170.10082.502@pc.kolivas.org> (raw)
In-Reply-To: <416211A3.8060806@yahoo.com.au>
Nick Piggin writes:
> Con Kolivas wrote:
>
>> Chen, Kenneth W writes:
>>
>>> Update p->timestamp to "now" in activate_task() doesn't look right
>>> to me at all. p->timestamp records last time it was running on a
>>> cpu. activate_task shouldn't update that variable when it queues
>>> a task on the runqueue.
>>>
>>> This bug (and combined with others) triggers improper load balancing.
>>
>>
>> The updated timestamp was placed there by Ingo to detect on-runqueue
>> time. If it is being used for load balancing then it is being used in
>> error.
>>
>
> Load balancing wants to know if a task is considered cache hot.
Yes I know. It used to be performed based on jiffies which was adequate
resolution for cache warmth at the time. The timestamp was being used for on
runqueue length measurement before the load balancing was modified to use
that value.
Con
next prev parent reply other threads:[~2004-10-05 4:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-05 2:16 Chen, Kenneth W
2004-10-05 2:34 ` Con Kolivas
2004-10-05 3:14 ` Nick Piggin
2004-10-05 4:45 ` Con Kolivas [this message]
2004-10-05 5:05 ` Peter Williams
2004-10-05 6:10 ` Nick Piggin
2004-10-05 6:31 ` Ingo Molnar
2004-10-05 6:36 ` Con Kolivas
2004-10-05 6:54 ` Ingo Molnar
2004-10-05 6:59 ` Con Kolivas
2004-10-05 7:08 ` Nick Piggin
2004-10-05 7:09 ` Ingo Molnar
2004-10-05 17:30 ` Chen, Kenneth W
2004-10-05 17:25 ` Chen, Kenneth W
2004-10-05 6:57 ` Nick Piggin
2004-10-05 8:19 ` Ingo Molnar
2004-10-05 17:44 ` Chen, Kenneth W
2004-10-05 22:46 Chen, Kenneth W
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