From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
To: Peter Williams <pwil3058@bigpond.net.au>
Cc: Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Con Kolivas <kernel@kolivas.org>,
"Siddha, Suresh B" <suresh.b.siddha@intel.com>,
"Chen, Kenneth W" <kenneth.w.chen@intel.com>,
Mike Galbraith <efault@gmx.de>,
linux-kernel@vger.kernel.org
Subject: more smpnice patch issues
Date: Fri, 24 Mar 2006 15:45:59 -0800 [thread overview]
Message-ID: <20060324154558.A20018@unix-os.sc.intel.com> (raw)
In-Reply-To: <4421F702.5040609@bigpond.net.au>; from pwil3058@bigpond.net.au on Wed, Mar 22, 2006 at 05:16:50PM -0800
more issues with smpnice patch...
a) consider a 4-way system (simple SMP system with no HT and cores) scenario
where a high priority task (nice -20) is running on P0 and two normal
priority tasks running on P1. load balance with smp nice code
will never be able to detect an imbalance and hence will never move one of
the normal priority tasks on P1 to idle cpus P2 or P3.
b) smpnice seems to break this patch..
[PATCH] sched: allow the load to grow upto its cpu_power
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0c117f1b4d14380baeed9c883f765ee023da8761
example scenario for this case: consider a numa system with two nodes, each
node containing four processors. if there are two processes in node-0 and with
node-1 being completely idle, your patch will move one of those processes to
node-1 whereas the previous behavior will retain those two processes in node-0..
(in this case, in your code max_load will be less than busiest_load_per_task)
smpnice patch has complicated the load balance code... Very difficult
to comprehend the side effects of this patch in the presence of different
priority tasks...
thanks,
suresh
next prev parent reply other threads:[~2006-03-24 23:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-22 23:51 cpu scheduler merge plans Andrew Morton
2006-03-22 22:57 ` kernel
2006-03-23 1:37 ` Siddha, Suresh B
2006-03-23 22:06 ` Peter Williams
2006-03-23 0:31 ` Nick Piggin
2006-03-23 1:16 ` Peter Williams
2006-03-24 23:45 ` Siddha, Suresh B [this message]
2006-03-25 0:56 ` more smpnice patch issues Peter Williams
2006-03-25 1:53 ` Peter Williams
2006-03-25 3:40 ` [PATCH] sched: make sure busiest group and run queue are pullable Peter Williams
2006-03-26 23:24 ` more smpnice patch issues Peter Williams
2006-03-26 23:43 ` [PATCH] sched: smpnice prevent integer arithmetic wrap problems Peter Williams
2006-03-23 5:03 ` cpu scheduler merge plans Ingo Molnar
2006-03-23 5:13 ` Andrew Morton
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