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>

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
 /*