lkml.org 
[lkml]   [2016]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature
From
Date


On 11/07/2016 09:16 PM, Steven Rostedt wrote:
> I'm confused? Are you saying that RR tasks don't get throttled in the
> current code? That sounds like a bug to me.

If the RT_RUNTIME_SHARING is enabled, the CPU in which the RR tasks are
running (and pinned) will borrow RT runtime from another CPU, allowing
the RR tasks to run forever. For example:

[root@kiron debug]# cat /proc/sched_debug | grep rt_runtime
.rt_runtime : 950.000000
.rt_runtime : 950.000000
.rt_runtime : 950.000000
.rt_runtime : 950.000000
[root@kiron debug]# echo RT_RUNTIME_SHARE > sched_features
[root@kiron debug]# taskset -c 2 chrt -r 5 /home/bristot/f &
[1] 23908
[root@kiron debug]# taskset -c 2 chrt -r 5 /home/bristot/f &
[2] 23915
[root@kiron debug]# cat /proc/sched_debug | grep rt_runtime
.rt_runtime : 900.000000
.rt_runtime : 950.000000
.rt_runtime : 1000.000000
.rt_runtime : 950.000000

You see? the rt_runtime of the CPU 2 was borrowed time from CPU 0.

It is not a BUG but a feature (no jokes haha). With RT_RUNTIME_SHARE,
the rt_runtime is such a global runtime. It works fine for tasks that
can migrate... but that is not the case for per-cpu kworkers.

-- Daniel

\
 
 \ /
  Last update: 2016-11-07 21:33    [W:0.190 / U:0.444 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site