From fafe870f31212a72f3c2d74e7b90e4ef39e83ee1 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 6 May 2015 18:04:24 +0200 Subject: context_tracking: Inherit TIF_NOHZ through forks instead of context switches TIF_NOHZ is used by context_tracking to force syscall slow-path on every task in order to track userspace roundtrips. As such, it must be set on all running tasks. It's currently explicitly inherited through context switches. There is no need to do it in this fast-path though. The flag could simply be set once for all on all tasks, whether they are running or not. Lets do this by setting the flag for the init task on early boot, and let it propagate through fork inheritance. While at it, mark context_tracking_cpu_set() as init code, we only need it at early boot time. Suggested-by: Oleg Nesterov Signed-off-by: Frederic Weisbecker Reviewed-by: Rik van Riel Cc: Borislav Petkov Cc: Chris Metcalf Cc: Dave Jones Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fe22f7510bce..54f032cea040 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2332,7 +2332,6 @@ context_switch(struct rq *rq, struct task_struct *prev, */ spin_release(&rq->lock.dep_map, 1, _THIS_IP_); - context_tracking_task_switch(prev, next); /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); barrier(); -- cgit v1.2.3 From 8cb9764fc88b41db11f251e8b2a0d006578b7eb4 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Wed, 6 May 2015 18:04:26 +0200 Subject: nohz: Set isolcpus when nohz_full is set nohz_full is only useful with isolcpus are also set, since otherwise the scheduler has to run periodically to try to determine whether to steal work from other cores. Accordingly, when booting with nohz_full=xxx on the command line, we should act as if isolcpus=xxx was also set, and set (or extend) the isolcpus set to include the nohz_full cpus. Signed-off-by: Chris Metcalf Signed-off-by: Frederic Weisbecker Acked-by: Rik van Riel Acked-by: Mike Galbraith Acked-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Dave Jones Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Rafael J. Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-5-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 54f032cea040..b8f48763579b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7036,6 +7036,9 @@ void __init sched_init_smp(void) alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL); alloc_cpumask_var(&fallback_doms, GFP_KERNEL); + /* nohz_full won't take effect without isolating the cpus. */ + tick_nohz_full_add_cpus_to(cpu_isolated_map); + sched_init_numa(); /* -- cgit v1.2.3