From d59cfc09c32a2ae31f1c3bc2983a0cd79afb3f14 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 13 May 2015 16:35:17 -0400 Subject: sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem The cgroup side of threadgroup locking uses signal_struct->group_rwsem to synchronize against threadgroup changes. This per-process rwsem adds small overhead to thread creation, exit and exec paths, forces cgroup code paths to do lock-verify-unlock-retry dance in a couple places and makes it impossible to atomically perform operations across multiple processes. This patch replaces signal_struct->group_rwsem with a global percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader side and contained in cgroups proper. This patch converts one-to-one. This does make writer side heavier and lower the granularity; however, cgroup process migration is a fairly cold path, we do want to optimize thread operations over it and cgroup migration operations don't take enough time for the lower granularity to matter. Signed-off-by: Tejun Heo Cc: Ingo Molnar Cc: Peter Zijlstra --- init/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index dc24dec60232..b9b824bf8f6b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -938,6 +938,7 @@ config NUMA_BALANCING_DEFAULT_ENABLED menuconfig CGROUPS bool "Control Group support" select KERNFS + select PERCPU_RWSEM help This option adds support for grouping sets of processes together, for use with process control subsystems such as Cpusets, CFS, memory -- cgit v1.2.3