Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 21/22] rcu: Allow RCU grace-period cleanup to be preempted | Date | Fri, 22 Jun 2012 08:17:20 -0700 |
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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
RCU grace-period cleanup is currently carried out with interrupts disabled, which can result in excessive latency spikes on large systems (many hundreds or thousands of CPUs). This patch therefore makes the RCU grace-period cleanup be preemptible, including voluntary preemption points, which should eliminate those latency spikes. Similar spikes from forcing of quiescent states will be dealt with similarly by later patches.
Reported-by: Mike Galbraith <mgalbraith@suse.de> Reported-by: Dimitri Sivanich <sivanich@sgi.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- kernel/rcutree.c | 11 +++++------ 1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 4a3f6b0..d21c2d3 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1160,7 +1160,7 @@ static int rcu_gp_kthread(void *arg) * completed. */ if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); /* * Propagate new ->completed value to rcu_node @@ -1169,14 +1169,13 @@ static int rcu_gp_kthread(void *arg) * to process their callbacks. */ rcu_for_each_node_breadth_first(rsp, rnp) { - /* irqs already disabled. */ - raw_spin_lock(&rnp->lock); + raw_spin_lock_irqsave(&rnp->lock, flags); rnp->completed = rsp->gpnum; - /* irqs remain disabled. */ - raw_spin_unlock(&rnp->lock); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + cond_resched(); } rnp = rcu_get_root(rsp); - raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + raw_spin_lock_irqsave(&rnp->lock, flags); } rsp->completed = rsp->gpnum; /* Declare grace period done. */ -- 1.7.8
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