linux-kernel - Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit

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Message-Id: <20170615215717.GI3721@linux.vnet.ibm.com>
Date:   Thu, 15 Jun 2017 14:57:17 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     peterz@...radead.org, oleg@...hat.com, josh@...htriplett.org,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        jiangshanlai@...il.com, paul.gortmaker@...driver.com,
        ebiederm@...ssion.com, dmitry.torokhov@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads
 explicit

On Thu, Jun 15, 2017 at 11:48:18AM -0700, Luis R. Rodriguez wrote:
> While reviewing RCU's interruptible swaits I noticed signals were actually
> not expected. Paul explained that the reason signals are not expected is
> we use kthreads, which don't get signals, furthermore the code avoided the
> uninterruptible swaits as otherwise it would contribute to the system load
> average on idle, bumping it from 0 to 2 or 3 (depending on preemption).
> 
> Since this can be confusing its best to be explicit about the requirements and
> goals. This patch depends on the other killable swaits [0] recently proposed as
> well interms of context. Thee patch can however be tested independently if
> the hunk is addressed separately.
> 
> [0] https://lkml.kernel.org/r/20170614222017.14653-3-mcgrof@kernel.org

Tested-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Are you looking to push these or were you wanting me to?

							Thanx, Paul

> Luis R. Rodriguez (2):
>   swait: add idle variants which don't contribute to load average
>   rcu: use idle versions of swait to make idle-hack clear
> 
>  include/linux/swait.h | 25 +++++++++++++++++++++++++
>  kernel/rcu/tree.c     |  4 ++--
>  2 files changed, 27 insertions(+), 2 deletions(-)
> 
> -- 
> 2.11.0
>