Re: [Resend PATCH v8 0/4] sched: Rewrite runnable load and utilization average tracking
From: Boqun Feng
Date: Wed Jun 17 2015 - 09:06:27 EST
On Wed, Jun 17, 2015 at 11:11:01AM +0800, Yuyang Du wrote:
> The sched_debug is informative, lets first give it some analysis.
> The workload is 12 CPU hogging tasks (always runnable) and 1 dbench
> task doing fs ops (70% runnable) running at the same time.
> Actually, these 13 tasks are in a task group /autogroup-9617, which
> has weight 1024.
> So the 13 tasks at most can contribute to an average of 79 (=1024/13)
> So the problem is:
> 1) The tasks in the workload have too small weight (only 79), because
> they share a task group.
> 2) Probably some "high" weight task even runnable a small time
> contribute "big" to cfs_rq's load_avg.
Thank you for your analysis.
I created a task group /g and set /g/cpu.shares to 13312 (1024 * 13),
and then ran `stress --cpu 12` and `dbench 1` simultaneously in that
group. The situation is much better, only one CPU is not fully loaded,
and its utilization rate stays around 85%.
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