Paul E. McKenney 8932a63d5e rcu: Reduce cache-miss initialization latencies for large systems ... Commit #0209f649 (rcu: limit rcu_node leaf-level fanout) set an upper limit of 16 on the leaf-level fanout for the rcu_node tree. This was needed to reduce lock contention that was induced by the synchronization of scheduling-clock interrupts, which was in turn needed to improve energy efficiency for moderate-sized lightly loaded servers. However, reducing the leaf-level fanout means that there are more leaf-level rcu_node structures in the tree, which in turn means that RCU's grace-period initialization incurs more cache misses. This is not a problem on moderate-sized servers with only a few tens of CPUs, but becomes a major source of real-time latency spikes on systems with many hundreds of CPUs. In addition, the workloads running on these large systems tend to be CPU-bound, which eliminates the energy-efficiency advantages of synchronizing scheduling-clock interrupts. Therefore, these systems need maximal values for the rcu_node leaf-level fanout. This commit addresses this problem by introducing a new kernel parameter named RCU_FANOUT_LEAF that directly controls the leaf-level fanout. This parameter defaults to 16 to handle the common case of a moderate sized lightly loaded servers, but may be set higher on larger systems. Reported-by: Mike Galbraith <efault@gmx.de> Reported-by: Dimitri Sivanich <sivanich@sgi.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>		2012-04-24 20:54:52 -07:00
..
calibrate.c	init: check printed flag to skip printing message	2012-03-23 16:58:38 -07:00
do_mounts.c	init/do_mounts.c: print error code on mount failure	2012-03-23 16:58:38 -07:00
do_mounts.h
do_mounts_initrd.c	get rid of pointless includes of ext2_fs.h	2012-03-31 16:03:15 -04:00
do_mounts_md.c
do_mounts_rd.c	new helper: ext2_image_size()	2012-03-31 16:03:16 -04:00
initramfs.c	init/initramfs.c: should use umode_t	2012-01-03 22:55:14 -05:00
Kconfig	rcu: Reduce cache-miss initialization latencies for large systems	2012-04-24 20:54:52 -07:00
main.c	Disintegrate and delete asm/system.h	2012-03-28 15:58:21 -07:00
Makefile
noinitramfs.c
version.c