lkml.org 
[lkml]   [2013]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 5/7] sched: compute runnable load avg in cpu_load and cpu_avg_load_per_task
> 
> blocked_load_avg is the expected "to wake" contribution from tasks
> already assigned to this rq.
>
> e.g. this could be:
> load = this_rq->cfs.runnable_load_avg + this_rq->cfs.blocked_load_avg;

Current load balance doesn't consider slept task's load which is
represented by blocked_load_avg. And the slept task is not on_rq, so
consider it in load balance is a little strange.

But your concern is worth to try. I will change the patchset and give
the testing results.

>
> Although, in general I have a major concern with the current implementation:
>
> The entire reason for stability with the bottom up averages is that
> when load migrates between cpus we are able to migrate it between the
> tracked sums.
>
> Stuffing observed averages of these into the load_idxs loses that
> mobility; we will have to stall (as we do today for idx > 0) before we
> can recognize that a cpu's load has truly left it; this is a very
> similar problem to the need to stably track this for group shares
> computation.
>
> To that end, I would rather see the load_idx disappear completely:
> (a) We can calculate the imbalance purely from delta (runnable_avg +
> blocked_avg)
> (b) It eliminates a bad tunable.

I also show the similar concern of load_idx months ago. seems overlooked. :)
>
>> - return cpu_rq(cpu)->load.weight;
>> + return (unsigned long)cpu_rq(cpu)->cfs.runnable_load_avg;
>
> Isn't this going to truncate on the 32-bit case?

I guess not, the old load.weight is unsigned long, and runnable_load_avg
is smaller than the load.weight. so it should be fine.

btw, according to above reason, guess move runnable_load_avg to
'unsigned long' type is ok, do you think so?
>

--
Thanks
Alex


\
 
 \ /
  Last update: 2013-05-06 17:43    [W:0.099 / U:1.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site