[lkml]   [2018]   [Mar]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle_select()
On 2018-03-21 23:15, Rafael J. Wysocki wrote:
> On Wed, Mar 21, 2018 at 6:59 PM, Thomas Ilsche
> <> wrote:
>> On 2018-03-21 15:36, Rafael J. Wysocki wrote:
>>> So please disregard this one entirely and take the v7.2 replacement
>>> instead of it:
>>> The current versions (including the above) is in the git branch at
>>> git:// \
>>> idle-loop-v7.2
>> With v7.2 (tested on SKL-SP from git) I see similar behavior in idle
>> as with v5: several cores which just keep the sched tick enabled.
>> Worse yet, some go only in C1 (not even C1E!?) despite sleeping the
>> full sched tick.
>> The resulting power consumption is ~105 W instead of ~ 70 W.
>> I have briefly ran v7 and I believe it was also affected.
> Then it looks like menu_select() stubbornly thinks that the idle
> duration will be within the tick boundary on those cores.
> That may be because the bumping up of the correction factor in
> menu_reflect() is too conservative or it may be necessary to do
> something radical to measured_us in menu_update() in case of a tick
> wakeup combined with a large next_timer_us value.
> For starters, please see if the attached patch (on top of the
> idle-loop-v7.2 git branch) changes this behavior in any way.

The patch on top of idle-loop-v7.2 doesn't improve idle behavior on
SKL-SP. Overall it is pretty erratic, I have not seen any regular
patterns. Sometimes only few cpus are affected, here's a screenshot of
almost all cpus being affected after a short burst workload.

 \ /
  Last update: 2018-03-22 14:20    [W:0.089 / U:2.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site