Re: [patch 0/7] sched: change nohz idle load balancing logic to pushmodel

From: Nigel Cunningham
Date: Thu May 20 2010 - 07:35:59 EST


On 20/05/10 21:17, Dominik Brodowski wrote:

On Thu, May 20, 2010 at 09:07:42PM +1000, Nigel Cunningham wrote:
"Load balancing tick" is still number one in my powertop list of top
causes of wakeups (sitting at ~60 to 80 per second as I type this, with
~170 wakeups per second total). Comparing this to the numbers I posted
earlier, we seem to have a win.

I do wonder, though, whether further work could still be done. If I take
one core offline, for example, I'm still getting load balancing ticks.
Intuitively, I'd expect there to be no need for them with only one core
available. But maybe I'm just ignorant of what's going on.

Are you using HZ=1000, and is the CPU active ~ 6-8 % ? If so, is it just the
regular timer tick while the CPU is active, and so not a real "wakeup"? (Or
possibly double the number if both CPUs are active)

HZ is 1000, and the CPU running percentage in Powertop is low (2% when I'm not typing).


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