From: Paul E. McKenney Date: Thu, 19 Feb 2015 18:51:32 +0000 (-0800) Subject: rcu: Add Kconfig option to expedite grace periods during boot X-Git-Tag: omap-for-v4.1/fixes-rc1~158^2~2^2^4~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ee42571f4381f184e2672dd34ab411e5bf5bd5e0;p=pandora-kernel.git 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 --- Reading git-diff-tree failed