linux-kernel - Re: [PATCH v5 0/2] sched: consider missed ticks when updating cpu load

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Date:	Wed, 11 Nov 2015 18:38:10 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	mingo@...nel.org, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org, efault@....de, tglx@...utronix.de,
	fweisbec@...il.com
Subject: Re: [PATCH v5 0/2] sched: consider missed ticks when updating cpu
 load

On Tue, Nov 10, 2015 at 09:36:00AM +0900, byungchul.park@....com wrote:
> From: Byungchul Park <byungchul.park@....com>
> 
> change from v4 to v5
> - fix comments and commit message
> - take new_load into account in update_cpu_load_nohz() and __update_cpu_load()
>   because it's non-zero in NOHZ_FULL
> 
> change from v3 to v4
> - focus the problem on full NOHZ
> 
> change from v2 to v3
> - add a patch which make __update_cpu_load() handle active tickless
> 
> change from v1 to v2
> - add some additional commit message (logic is same exactly)
> 
> additionally i tried to use the return value of hrtimer_forward() instead of
> jiffies to get pending tick for updating cpu load. it's easy for
> update_cpu_load_nohz() to do that. but for update_idle_cpu_load(), i need
> more time to think about how to implement it nicely.

Actually because of update_idle_load() which is used when doing nohz
load balancing while the cpu has been still tick-stopped, this looks
not be able to be implemented without any kind of last_update_xxx
variable. What do you think about it, Peter?

> 
> and i will try to fix other stuffs caused by full NOHZ later with another
> patch. i decided to send this patch at first because "cpu load update" is a
> standalone problem which is not coupled with other stuffs.
> 
> Byungchul Park (2):
>   sched: make __update_cpu_load() handle NOHZ_FULL tickless
>   sched: make update_cpu_load_nohz() consider missed ticks in NOHZ_FULL
> 
>  include/linux/sched.h    |    4 ++--
>  kernel/sched/fair.c      |   57 +++++++++++++++++++++++++++++++++++++---------
>  kernel/time/tick-sched.c |    8 +++----
>  3 files changed, 52 insertions(+), 17 deletions(-)
> 
> -- 
> 1.7.9.5
> 
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