From mboxrd@z Thu Jan 1 00:00:00 1970 From: khilman@linaro.org (Kevin Hilman) Date: Sun, 27 Oct 2013 18:32:26 -0700 Subject: [tip:timers/core] ARM: Kconfig: allow full nohz CPU accounting In-Reply-To: <20131018163740.GA21983@codeaurora.org> References: <20131016121416.GD12773@localhost.localdomain> <20131018163740.GA21983@codeaurora.org> Message-ID: <526DBEAA.4030707@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Stephen, On 10/18/2013 09:37 AM, Stephen Boyd wrote: > On 10/16, Frederic Weisbecker wrote: >> On Thu, Oct 03, 2013 at 06:58:03AM -0700, tip-bot for Kevin Hilman wrote: >>> Commit-ID: 31c1fc8187158cb80ccd57c19e024c55af901797 >>> Gitweb: http://git.kernel.org/tip/31c1fc8187158cb80ccd57c19e024c55af901797 >>> Author: Kevin Hilman >>> AuthorDate: Mon, 16 Sep 2013 15:28:22 -0700 >>> Committer: Frederic Weisbecker >>> CommitDate: Mon, 30 Sep 2013 15:37:05 +0200 >>> >>> ARM: Kconfig: allow full nohz CPU accounting >>> >>> With the 64-bit requirement removed from VIRT_CPU_ACCOUNTING_GEN, >>> allow ARM platforms to enable it. Since VIRT_CPU_ACCOUNTING_GEN is a >>> dependency for full NO_HZ, this allows ARM platforms to enable full >>> NO_HZ as well. >> >> I realize that arm doesn't implement irq work raise. It hooks on the >> timer to execute pending irq work. You'll need to implement arch_irq_work_raise() >> and implement some sort of self IPI to trigger irq work. The full dynticks subsystem >> relies on that to work correctly. It often use that to re-evaluate and possibly restart >> the tick after scheduler, posix timer updates, etc... >> >> That notwithstanding that if you have no tick, tick based irq work can't >> work. >> > > Something like this? The only problem is that this latches on to > the SMP support for IPIs. If CONFIG_SMP is disabled we won't get > arch_irq_work_raise() but perhaps that isn't so big of a deal? Or > we should think about exposing IPI support to UP systems on ARM. Care to submit a proper patch for this to LAKML? or if you prefer I can do it (keeping your authorship.) We need this for proper full NOHZ support on ARM. Thanks. Kevin