From ee42571f4381f184e2672dd34ab411e5bf5bd5e0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 19 Feb 2015 10:51:32 -0800 Subject: rcu: Add Kconfig option to expedite grace periods during boot This commit adds a CONFIG_RCU_EXPEDITE_BOOT Kconfig parameter that emulates a very early boot rcu_expedite_gp(). A late-boot call to rcu_end_inkernel_boot() will provide the corresponding rcu_unexpedite_gp(). The late-boot call to rcu_end_inkernel_boot() should be made just before init is spawned. According to Arjan: > To show the boot time, I'm using the timestamp of the "Write protecting" > line, that's pretty much the last thing we print prior to ring 3 execution. > > A kernel with default RCU behavior (inside KVM, only virtual devices) > looks like this: > > [ 0.038724] Write protecting the kernel read-only data: 10240k > > a kernel with expedited RCU (using the command line option, so that I > don't have to recompile between measurements and thus am completely > oranges-to-oranges) > > [ 0.031768] Write protecting the kernel read-only data: 10240k > > which, in percentage, is an 18% improvement. Reported-by: Arjan van de Ven Signed-off-by: Paul E. McKenney Tested-by: Arjan van de Ven --- include/linux/rcupdate.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 57a4d1f73a00..b9f039b11d31 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -278,6 +278,7 @@ static inline int rcu_preempt_depth(void) /* Internal to kernel */ void rcu_init(void); +void rcu_end_inkernel_boot(void); void rcu_sched_qs(void); void rcu_bh_qs(void); void rcu_check_callbacks(int user); -- cgit v1.2.3