From mboxrd@z Thu Jan 1 00:00:00 1970 From: hanjun.guo@linaro.org (Hanjun Guo) Date: Thu, 15 Aug 2013 09:00:37 +0800 Subject: [RFC][PATCH 1/2] ARM64: add cpu topology definition In-Reply-To: <20130814112720.GB43445@MacBook-Pro.local> References: <1374921728-9007-1-git-send-email-hanjun.guo@linaro.org> <20130729095400.GB32383@mudshark.cambridge.arm.com> <20130814112720.GB43445@MacBook-Pro.local> Message-ID: <520C2835.6050001@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2013-8-14 19:27, Catalin Marinas wrote: > On Mon, Jul 29, 2013 at 10:54:01AM +0100, Will Deacon wrote: >> On Mon, Jul 29, 2013 at 10:46:06AM +0100, Vincent Guittot wrote: >>> On 27 July 2013 12:42, Hanjun Guo wrote: >>>> Power aware scheduling needs the cpu topology information to improve the >>>> cpu scheduler decision making. >>> >>> It's not only power aware scheduling. The scheduler already uses >>> topology and cache sharing when CONFIG_SCHED_MC and/or >>> CONFIG_SCHED_SMT are enable. So you should also add these configs for >>> arm64 so the scheduler can use it >> >> ... except that the architecture doesn't define what the AFF fields in MPIDR >> really represent. Using them to make key scheduling decisions relating to >> cache proximity seems pretty risky to me, especially given the track record >> we've seen already on AArch32 silicon. It's a convenient register if it >> contains the data we want it to contain, but we need to force ourselves to >> come to terms with reality here and simply use it as an identifier for a >> CPU. >> >> Can't we just use the device-tree to represent this topological data for >> arm64? Lorenzo has been working on bindings in this area. > > Catching up on email after holiday - I agree with Will here, we should > use DT for representing the topology (or ACPI) and not rely on the MPIDR > value. > Ok, I'm working on the ACPI part now, Thanks for your comments. Regards Hanjun