Increase default RCU batching sharply

Dipankar made RCU limit the batch size to improve latency, but that
approach is unworkable: it can cause the RCU queues to grow without
bounds, since the batch limiter ended up limiting the callbacks.

So make the limit much higher, and start planning on instead limiting
the batch size by doing RCU callbacks more often if the queue looks like
it might be growing too long.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index bef3b6901b7693e11ce2ddd0fa2ee4c1c00c566d..dd99415b1551b12d9421e7bdf738bbb7ae74002e 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -71,7 +71,7 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
 
 /* Fake initialization required by compiler */
 static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
-static int maxbatch = 10;
+static int maxbatch = 10000;
 
 #ifndef __HAVE_ARCH_CMPXCHG
 /*