From 2159197d66770ec01f75c93fb11dc66df81fd45b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 28 Apr 2016 12:49:38 +0200 Subject: [PATCH] sched/core: Enable increased load resolution on 64-bit kernels Mike ran into the low load resolution limitation on his big machine. So reenable these bits; nobody could ever reproduce/analyze the reported power usage claim and Google has been running with this for years as well. Reported-by: Mike Galbraith Tested-by: Mike Galbraith Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- kernel/sched/sched.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 0b6a838e9e73..066a4c2d2695 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -49,11 +49,13 @@ static inline void cpu_load_update_active(struct rq *this_rq) { } * and does not change the user-interface for setting shares/weights. * * We increase resolution only if we have enough bits to allow this increased - * resolution (i.e. BITS_PER_LONG > 32). The costs for increasing resolution - * when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the - * increased costs. + * resolution (i.e. 64bit). The costs for increasing resolution when 32bit are + * pretty high and the returns do not justify the increased costs. + * + * Really only required when CONFIG_FAIR_GROUP_SCHED is also set, but to + * increase coverage and consistency always enable it on 64bit platforms. */ -#if 0 /* BITS_PER_LONG > 32 -- currently broken: it increases power usage under light load */ +#ifdef CONFIG_64BIT # define SCHED_LOAD_RESOLUTION 10 # define scale_load(w) ((w) << SCHED_LOAD_RESOLUTION) # define scale_load_down(w) ((w) >> SCHED_LOAD_RESOLUTION) -- GitLab