From: Paul E. McKenney Date: Wed, 4 Jun 2014 20:46:03 +0000 (-0700) Subject: rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs X-Git-Tag: omap-for-v3.17/fixes-against-rc2~180^2^2~1^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c0f489d2c6fec8994c642c2ec925eb858727dc7b;p=pandora-kernel.git rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs Binding the grace-period kthreads to the timekeeping CPU resulted in significant performance decreases for some workloads. For more detail, see: https://lkml.org/lkml/2014/6/3/395 for benchmark numbers https://lkml.org/lkml/2014/6/4/218 for CPU statistics It turns out that it is necessary to bind the grace-period kthreads to the timekeeping CPU only when all but CPU 0 is a nohz_full CPU on the one hand or if CONFIG_NO_HZ_FULL_SYSIDLE=y on the other. In other cases, it suffices to bind the grace-period kthreads to the set of non-nohz_full CPUs. This commit therefore creates a tick_nohz_not_full_mask that is the complement of tick_nohz_full_mask, and then binds the grace-period kthread to the set of CPUs indicated by this new mask, which covers the CONFIG_NO_HZ_FULL_SYSIDLE=n case. The CONFIG_NO_HZ_FULL_SYSIDLE=y case still binds the grace-period kthreads to the timekeeping CPU. This commit also includes the tick_nohz_full_enabled() check suggested by Frederic Weisbecker. Reported-by: Jet Chen Signed-off-by: Paul E. McKenney [ paulmck: Created housekeeping_affine() and housekeeping_mask per fweisbec feedback. ] --- Reading git-diff-tree failed