linux-kernel - [PATCH] sched: check pinned tasks before nohz balance, linux-4.2-rc5

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Message-ID: <CA+KHdyVB8oTDih2xrQLz1ZGZgdaM6NR1hfeuyCvYw=GjiKzYgg@mail.gmail.com>
Date:	Wed, 5 Aug 2015 17:14:34 +0200
From:	Uladzislau Rezki <urezki@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...hat.com>, Mike Galbraith <efault@....de>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] sched: check pinned tasks before nohz balance, linux-4.2-rc5

While investigating “load balancer” logic, I run into interesting
behavior related
to affinity and NO_HZ idle balance. Basically saying if there are two
tasks running
in certain rq and one of them is pinned/affined, then scheduler will
trigger load
balance on power collapsed core via soft irq.

The corner case here is it may fail to unbalance because of affinity, as a
result core that has two tasks will interrupt any found idle one each its timer
tick, what can lead to wasting of power, especially in mobile area, what is
our case.

Do you have any concern with provided patch?

--
Uladzislau Rezki

View attachment "0001-sched-check-pinned-tasks-before-balance.patch" of type "text/x-patch" (3705 bytes)