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From: Bill Davidsen <davidsen@tmr.com>
To: Olof Johansson <olof@lixom.net>
Cc: Willy Tarreau <w@1wt.eu>, Mike Galbraith <efault@gmx.de>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: Scheduler(?) regression from 2.6.22 to 2.6.24 for short-lived threads
Date: Mon, 11 Feb 2008 16:45:12 -0500 [thread overview]
Message-ID: <47B0C1E8.2050809@tmr.com> (raw)
In-Reply-To: <20080210052941.GA4731@lixom.net>
Olof Johansson wrote:
>> However, I fail to understand the goal of the reproducer. Granted it shows
>> irregularities in the scheduler under such conditions, but what *real*
>> workload would spend its time sequentially creating then immediately killing
>> threads, never using more than 2 at a time ?
>>
>> If this could be turned into a DoS, I could understand, but here it looks
>> a bit pointless :-/
>
> It seems generally unfortunate that it takes longer for a new thread to
> move over to the second cpu even when the first is busy with the original
> thread. I can certainly see cases where this causes suboptimal overall
> system behaviour.
>
I think the moving to another CPU gets really dependent on the CPU type.
On a P4+HT the caches are shared, and moving costs almost nothing for
cache hits, while on CPUs which have other cache layouts the migration
cost is higher. Obviously multi-core should be cheaper than
multi-socket, by avoiding using the system memory bus, but it still can
get ugly.
I have an IPC test around which showed that, it ran like hell on HT, and
progressively worse as cache because less shared. I wonder why the
latest git works so much better?
--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
next prev parent reply other threads:[~2008-02-11 21:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-09 0:04 Olof Johansson
2008-02-09 0:08 ` Ingo Molnar
2008-02-09 0:32 ` Olof Johansson
2008-02-09 7:58 ` Mike Galbraith
2008-02-09 8:03 ` Willy Tarreau
2008-02-09 10:58 ` Mike Galbraith
2008-02-09 11:40 ` Willy Tarreau
2008-02-09 13:37 ` Mike Galbraith
2008-02-09 16:19 ` Willy Tarreau
2008-02-09 17:33 ` Mike Galbraith
2008-02-10 5:29 ` Olof Johansson
2008-02-10 6:15 ` Willy Tarreau
2008-02-10 7:00 ` Olof Johansson
2008-02-10 7:58 ` Willy Tarreau
2008-02-11 8:15 ` Mike Galbraith
2008-02-11 17:26 ` Olof Johansson
2008-02-11 19:58 ` Mike Galbraith
2008-02-11 20:31 ` Olof Johansson
2008-02-12 9:23 ` Mike Galbraith
2008-02-13 5:49 ` Mike Galbraith
2008-02-11 21:45 ` Bill Davidsen [this message]
2008-02-12 4:30 ` Mike Galbraith
[not found] <fa.6N2dhyJ1cmBqiuFKgCaYfwduM+0@ifi.uio.no>
2008-02-09 1:49 ` Robert Hancock
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