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 --- kernel/fork.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 03c1eaaa6ef5..9531275e12a9 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1144,10 +1144,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) tty_audit_fork(sig); sched_autogroup_fork(sig); -#ifdef CONFIG_CGROUPS - init_rwsem(&sig->group_rwsem); -#endif - sig->oom_score_adj = current->signal->oom_score_adj; sig->oom_score_adj_min = current->signal->oom_score_adj_min; -- cgit v1.2.3