From 37c72e56f6b234ea7387ba530434a80abf2658d8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 14 Oct 2009 10:15:55 -0700 Subject: rcu: Prevent RCU IPI storms in presence of high call_rcu() load As the number of callbacks on a given CPU rises, invoke force_quiescent_state() only every blimit number of callbacks (defaults to 10,000), and even then only if no other CPU has invoked force_quiescent_state() in the meantime. This should fix the performance regression reported by Nick. Reported-by: Nick Piggin Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: jens.axboe@oracle.com LKML-Reference: <12555405592133-git-send-email-> Signed-off-by: Ingo Molnar --- kernel/rcutree.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/rcutree.h') diff --git a/kernel/rcutree.h b/kernel/rcutree.h index b40ac5706040..599161f309fb 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -167,6 +167,10 @@ struct rcu_data { struct rcu_head *nxtlist; struct rcu_head **nxttail[RCU_NEXT_SIZE]; long qlen; /* # of queued callbacks */ + long qlen_last_fqs_check; + /* qlen at last check for QS forcing */ + unsigned long n_force_qs_snap; + /* did other CPU force QS recently? */ long blimit; /* Upper limit on a processed batch */ #ifdef CONFIG_NO_HZ -- cgit v1.2.3