From mboxrd@z Thu Jan 1 00:00:00 1970 From: fweisbec@gmail.com (Frederic Weisbecker) Date: Thu, 14 Nov 2013 12:42:56 +0100 Subject: a bug on NO_HZ_FULL_ALL In-Reply-To: <52848547.9080604@linaro.org> References: <52843855.5060509@linaro.org> <52847FBE.9070501@linaro.org> <52848547.9080604@linaro.org> Message-ID: <20131114114253.GA16501@localhost.localdomain> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Nov 14, 2013 at 01:39:43PM +0530, viresh kumar wrote: > On Thursday 14 November 2013 01:35 PM, Vincent Guittot wrote: > > AFAICT, It's a none issue. In full nohz, a timer fires periodically > > (around 4sec period on ARM IIRC) on one cpu (cpu0). > > Timer should always be running on CPU0, its out of nohz-full domain. Its > cpu 1, where it will fire after long delays.. > > > https://wiki.linaro.org/WorkingGroups/PowerManagement/Doc/AdaptiveTickless Right. CPU 0 stays pure periodic unless you select CONFIG_NO_HZ_FULL_SYSIDLE=y then it can be also nohz when the full system is idle. I strongly recommend for power consumption.