Messages in this thread | | | Subject | Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity | From | Luca Abeni <> | Date | Thu, 10 Dec 2015 14:27:39 +0100 |
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Hi Vincent,
first of all, thanks for adding me in the discussion.
On 12/09/2015 09:50 AM, Vincent Guittot wrote: > adding Lucas > > On 9 December 2015 at 07:19, Steve Muckle <steve.muckle@linaro.org> wrote: >> From: Vincent Guittot <vincent.guittot@linaro.org> >> >> Instead of monitoring the exec time of deadline tasks to evaluate the >> CPU capacity consumed by deadline scheduler class, we can directly >> calculate it thanks to the sum of utilization of deadline tasks on the >> CPU. We can remove deadline tasks from rt_avg metric and directly use >> the average bandwidth of deadline scheduler in scale_rt_capacity. >> >> Based in part on a similar patch from Luca Abeni <luca.abeni@unitn.it>. Just to check if my understanding of your patch is correct: what you do is to track the total utilisation of the tasks that are assigned to a CPU/core, independently from their state (active or inactive). The difference with my patch is that I try to track the "active utilisation" (eliminating the utilisation of the tasks that are blocked).
Is this understanding correct? If yes, I think your approach is safe (and easier to implement - modulo a small issue when a task terminates of switches to other scheduling policies; I think there already are some "XXX" comments in the current code). However, it allows to save less energy (or reclaim less CPU time). For example, if I create a SCHED_DEADLINE task with runtime 90ms and period 100ms it will not allow to scale the CPU frequency even if it never executes (because is always blocked).
[...] >> + /* This is the "average utilization" for this runqueue */ >> + s64 avg_bw; >> }; Small nit: why "average" utilization? I think a better name would be "runqueue utilization" or "local utilization", or something similar... If I understand correctly (sorry if I missed something), this is not an average, but the sum of the utilisations of the tasks on this runqueue... No?
Luca
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