From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sasl.smtp.pobox.com (a-sasl-fastnet.sasl.smtp.pobox.com [207.106.133.19]) by ozlabs.org (Postfix) with ESMTP id 94828DDEE1 for ; Thu, 19 Jun 2008 10:30:08 +1000 (EST) From: Nathan Lynch To: linux-kernel@vger.kernel.org Subject: [RFC/PATCH 0/3] sched: allow arch override of cpu power Date: Wed, 18 Jun 2008 19:29:31 -0500 Message-Id: <1213835374-10868-1-git-send-email-ntl@pobox.com> Cc: linuxppc-dev@ozlabs.org, Ingo Molnar , Paul Mackerras , Anton Blanchard List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , There is an "interesting" quality of POWER6 cores, which each have 2 hardware threads: assuming one thread on the core is idle, the primary thread is a little "faster" than the secondary thread. To illustrate: for cpumask in 0x1 0x2 ; do taskset $cpumask /usr/bin/time -f "%e elapsed, %U user, %S sys" \ /bin/sh -c "i=1000000 ; while (( i-- )) ; do : ; done" done 17.05 elapsed, 16.83 user, 0.22 sys 17.54 elapsed, 17.32 user, 0.22 sys (The first result is for a primary thread; the second result for a secondary thread.) So it would be nice to have the scheduler slightly prefer primary threads on POWER6 machines. These patches, which allow the architecture to override the scheduler's CPU "power" calculation, are one possible approach, but I'm open to others. Please note: these seemed to have the desired effect on 2.6.25-rc kernels (2-3% improvement in a kernbench-like make -j ), but I'm not seeing this improvement with 2.6.26-rc kernels for some reason I am still trying to track down. Nathan Lynch (3): sched: support arch override of sched_group cpu power add cpu_power to machdep_calls, override SD_SIBLING_INIT adjust cpu power for secondary threads on POWER6 arch/powerpc/kernel/setup-common.c | 7 ++++++ arch/powerpc/platforms/pseries/setup.c | 37 ++++++++++++++++++++++++++++++++ include/asm-powerpc/cputable.h | 3 +- include/asm-powerpc/machdep.h | 2 + include/asm-powerpc/topology.h | 31 ++++++++++++++++++++++++++ include/linux/sched.h | 1 + kernel/sched.c | 14 ++++++++++++ 7 files changed, 94 insertions(+), 1 deletions(-)