lkml.org 
[lkml]   [2016]   [Apr]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 4/6] sched/fair: Remove scale_load_down() for load_avg
On Tue, Apr 05, 2016 at 12:12:29PM +0800, Yuyang Du wrote:
> Currently, load_avg = scale_load_down(load) * runnable%. The extra scaling
> down of load does not make much sense, because load_avg is primarily THE
> load and on top of that, we take runnable time into account.
>
> We therefore remove scale_load_down() for load_avg. But we need to
> carefully consider the overflow risk if load has higher range
> (2*SCHED_FIXEDPOINT_SHIFT). The only case an overflow may occur due
> to us is on 64bit kernel with increased load range. In that case,
> the 64bit load_sum can afford 4251057 (=2^64/47742/88761/1024)
> entities with the highest load (=88761*1024) always runnable on one
> single cfs_rq, which may be an issue, but should be fine. Even if this
> occurs at the end of day, on the condition where it occurs, the
> load average will not be useful anyway.

I do feel we need a little more words on the actual ramification of
overflowing here.

Yes, having 4m tasks on a single runqueue will be somewhat unlikely, but
if it happens, then what will the user experience? How long (if ever)
does it take for numbers to correct themselves etc..

> Signed-off-by: Yuyang Du <yuyang.du@intel.com>
> [update calculate_imbalance]
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

This SoB Chain suggests you wrote it and Vincent send it on, yet this
email is from you and Vincent isn't anywhere. Something's not right.

\
 
 \ /
  Last update: 2016-04-28 12:41    [W:0.122 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site