From 030bdc3fd0807b6097a937468859f4b4baf1b950 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Sun, 6 Dec 2009 17:48:33 +0000 Subject: [PATCH] powerpc/defconfigs: Set HZ=100 on pseries and ppc64 defconfigs Now we have high res timers there is less of a reason for a high HZ value. Furthermore I think there a few reasons we should reduce HZ to 100: - Timer interrupt overhead. While this overhead is small, there are applications that are very sensitive to jitter (eg some HPC apps). - Issues with the timer wheel code. When coming out of NO_HZ idle we work our way through the timer code one tick at a time. If we have been idle a long time, this adds up - I sometimes see milliseconds of time spent in that loop. Long term we should fix the timer wheel algorithm, but for now if we reduce HZ then we reduce the amount of work the timer code has to do when coming out of idle. Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/configs/ppc64_defconfig | 6 +++--- arch/powerpc/configs/pseries_defconfig | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/configs/ppc64_defconfig b/arch/powerpc/configs/ppc64_defconfig index 4b043f973389..7b3804a6e363 100644 --- a/arch/powerpc/configs/ppc64_defconfig +++ b/arch/powerpc/configs/ppc64_defconfig @@ -304,11 +304,11 @@ CONFIG_TICK_ONESHOT=y CONFIG_NO_HZ=y CONFIG_HIGH_RES_TIMERS=y CONFIG_GENERIC_CLOCKEVENTS_BUILD=y -# CONFIG_HZ_100 is not set -CONFIG_HZ_250=y +CONFIG_HZ_100=y +# CONFIG_HZ_250 is not set # CONFIG_HZ_300 is not set # CONFIG_HZ_1000 is not set -CONFIG_HZ=250 +CONFIG_HZ=100 CONFIG_SCHED_HRTICK=y CONFIG_PREEMPT_NONE=y # CONFIG_PREEMPT_VOLUNTARY is not set diff --git a/arch/powerpc/configs/pseries_defconfig b/arch/powerpc/configs/pseries_defconfig index e89fccbb4a61..ca9ff9aad74a 100644 --- a/arch/powerpc/configs/pseries_defconfig +++ b/arch/powerpc/configs/pseries_defconfig @@ -230,11 +230,11 @@ CONFIG_TICK_ONESHOT=y CONFIG_NO_HZ=y CONFIG_HIGH_RES_TIMERS=y CONFIG_GENERIC_CLOCKEVENTS_BUILD=y -# CONFIG_HZ_100 is not set -CONFIG_HZ_250=y +CONFIG_HZ_100=y +# CONFIG_HZ_250 is not set # CONFIG_HZ_300 is not set # CONFIG_HZ_1000 is not set -CONFIG_HZ=250 +CONFIG_HZ=100 CONFIG_SCHED_HRTICK=y CONFIG_PREEMPT_NONE=y # CONFIG_PREEMPT_VOLUNTARY is not set -- GitLab