This patch makes RCU callbacks friendly to scheduler.  It helps low latency
by limiting the number of callbacks invoked per tasklet handler.  Since we
cannot schedule during a single softirq handler, this reduces size of
non-preemptible section significantly, specially under heavy RCU updates.
The limiting is done through a kernel parameter rcupdate.maxbatch which is
the maximum number of RCU callbacks to invoke during a single tasklet
handler.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>