From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Galbraith <efault@gmx.de>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Clark Williams <clark@redhat.com>,
Andrew Theurer <habanero@us.ibm.com>
Subject: Re: [RFC] sched: The removal of idle_balance()
Date: Mon, 18 Feb 2013 13:43:45 +0530 [thread overview]
Message-ID: <20130218081345.GA4157@linux.vnet.ibm.com> (raw)
In-Reply-To: <1360908819.23152.97.camel@gandalf.local.home>
> The cache misses dropped by ~23% and migrations dropped by ~28%. I
> really believe that the idle_balance() hurts performance, and not just
> for something like hackbench, but the aggressive nature for migration
> that idle_balance() causes takes a large hit on a process' cache.
>
> Think about it some more, just because we go idle isn't enough reason to
> pull a runable task over. CPUs go idle all the time, and tasks are woken
> up all the time. There's no reason that we can't just wait for the sched
> tick to decide its time to do a bit of balancing. Sure, it would be nice
> if the idle CPU did the work. But I think that frame of mind was an
> incorrect notion from back in the early 2000s and does not apply to
> today's hardware, or perhaps it doesn't apply to the (relatively) new
> CFS scheduler. If you want aggressive scheduling, make the task rt, and
> it will do aggressive scheduling.
>
How is it that the normal tick based load balancing gets it correctly while
the idle_balance gets is wrong? Can it because of the different
cpu_idle_type?
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2013-02-18 8:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-15 6:13 [RFC] sched: The removal of idle_balance() Steven Rostedt
2013-02-15 7:26 ` Mike Galbraith
2013-02-15 12:07 ` Peter Zijlstra
2013-02-15 12:21 ` Peter Zijlstra
2013-02-15 12:32 ` Mike Galbraith
2013-02-16 16:12 ` Steven Rostedt
2013-02-17 6:26 ` Mike Galbraith
2013-02-17 7:14 ` Mike Galbraith
2013-02-17 21:54 ` Steven Rostedt
2013-02-18 3:42 ` Mike Galbraith
2013-02-18 15:23 ` Steven Rostedt
2013-02-18 17:22 ` Mike Galbraith
2013-02-15 7:45 ` Joonsoo Kim
2013-02-15 15:05 ` Steven Rostedt
2013-02-17 6:26 ` Mike Galbraith
2013-02-18 8:13 ` Srikar Dronamraju [this message]
2013-02-18 15:25 ` Steven Rostedt
2013-02-19 4:13 ` Rakib Mullick
2013-02-19 7:29 ` Michael Wang
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