Hi Viresh,
(1) Recently I have done a lot of testing for the new RCU functionality (new RCU FNOHZ implementation, updated RCU no-callback implementation) which is scheduled for 3.11/3.12 mainline. In my tests it helped to keep the A15's quiet and showed power savings for some workloads.
During last Linaro Connect people started to ask me if we can bring these features in already earlier.
Would it be possible for you to merge in 'idlenocb.2013.03.18b' (based on v3.9-rc2) (or newer) from 'git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git' into your big.LITTLE MP tree? I talked to Paul McKenney about this and he would like to have this additional test coverage.
I have performed the following tests: System comes up and pm-qa (cpufreq, cpuidle, cpuhotplug) on nano and FTS (mpbasic, mpcore, mpextended, mploadbalance, mpregression, pmump) on Android FS look good.
(2) On top of the merge, we must assure that the TC2 default config file gets changed:
Change the config file: * Set CONFIG_RCU_FAST_NO_HZ=y * Set CONFIG_RCU_NOCB_CPU=y * Set CONFIG_RCU_NOCB_CPU_ALL=y
diff -Naur config_orig .config --- config_orig 2013-03-13 14:15:10.574248125 +0000 +++ .config 2013-03-13 14:15:34.334248346 +0000 @@ -93,9 +93,12 @@ CONFIG_RCU_FANOUT=32 CONFIG_RCU_FANOUT_LEAF=16 # CONFIG_RCU_FANOUT_EXACT is not set -# CONFIG_RCU_FAST_NO_HZ is not set +CONFIG_RCU_FAST_NO_HZ=y # CONFIG_TREE_RCU_TRACE is not set -# CONFIG_RCU_NOCB_CPU is not set +CONFIG_RCU_NOCB_CPU=y +# CONFIG_RCU_NOCB_CPU_NONE is not set +# CONFIG_RCU_NOCB_CPU_ZERO is not set +CONFIG_RCU_NOCB_CPU_ALL=y CONFIG_IKCONFIG=y CONFIG_IKCONFIG_PROC=y CONFIG_LOG_BUF_SHIFT=16
Cheers,
-- Dietmar
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