[PATCH 3.13, 3.14, 3.16, 3.17] rcu: Reduce rcu kthread wakeups

Pranith Kumar bobby.prani at gmail.com
Mon Oct 13 20:24:35 UTC 2014

On Mon, Oct 13, 2014 at 4:01 PM, Kamal Mostafa <kamal at canonical.com> wrote:
> On Mon, 2014-10-13 at 12:29 -0400, Pranith Kumar wrote:
>> Backport 2aa792e and parts of 48a7639 to 3.13 which is Ubuntu LTS kernel.
>> This commit reduces the number of rcu kthread wakeups. Tested for over a week on
>> my desktop 14.04 system.
>> Signed-off-by: Pranith Kumar <bobby.prani at gmail.com>
>> CC: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> Hi Pranith and Paul-
> This looks good, but how about lets split it back into two commits (the
> second a clean cherry-pick) and submit it for 3.{14,16,17}-stable also:
> 3.13 and 3.14 could apply the attached 48a7639 mini-backport (just
> supplying rcu_gp_kthread_wake), and then cherry-pick 2aa792e.
> 3.16 and 3.17 carry 48a7639 already, so could just cherry-pick 2aa792e.

The patch looks good. The commit message can be trimmed to just the last para:

Add a new rcu_gp_kthread_wake() which wakes up the gp kthread when it
is necessary and safe to do so: No self-wakes, no wake-ups if the
->gp_flags field indicates there is no need (as in someone else did
the wake-up before we got around to it),  and no wake-ups before the
grace-period kthread has been created.


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