From: Juri Lelli <juri.lelli@arm.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: peterz@infradead.org, mingo@kernel.org,
linux-kernel@vger.kernel.org, juri.lelli@gmail.com,
rostedt@goodmis.org, kernel-team@lge.com
Subject: Re: [PATCH 0/8] sched/deadline: Return the best satisfying affinity and dl in cpudl_find
Date: Mon, 27 Mar 2017 15:05:07 +0100 [thread overview]
Message-ID: <20170327140507.GN10289@e106622-lin> (raw)
In-Reply-To: <1490265163-29981-1-git-send-email-byungchul.park@lge.com>
Hi,
On 23/03/17 19:32, Byungchul Park wrote:
> cpudl_find() is used to find a cpu having the latest dl. The function
> should return the latest cpu among ones satisfying task's affinity and
> dl constraint, but current code gives up immediately and just return
> fail when it fails at the test *only with* the maximum cpu.
>
> For example:
>
> cpu 0 is running a task (dl: 10).
> cpu 1 is running a task (dl: 9).
> cpu 2 is running a task (dl: 8).
> cpu 3 is running a task (dl: 2).
>
> where cpu 3 want to push a task (affinity is 1 2 3 and dl is 1).
Hummm, but this should only happen if you disable admission control,
right? Otherwise task's affinity can't be smaller that 0-3.
>
> In this case, the task should be migrated from cpu 3 to cpu 1, and
> preempt cpu 1's task. However, current code just returns fail because
> it fails at the affinity test with the maximum cpu, that is, cpu 0.
>
> This patch set tries to find the best among ones satisfying task's
> affinity and dl constraint until success or no more to see.
>
Anyway, do you have numbers showing how common is you fail scenario?
It would be interesting to understand how much the slow path is actually
used, IMHO.
Thanks,
- Juri
next prev parent reply other threads:[~2017-03-27 14:07 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-23 10:32 [PATCH 0/8] sched/deadline: Return the best satisfying affinity and dl in cpudl_find Byungchul Park
2017-03-23 10:32 ` [PATCH 1/8] sched/deadline: Make find_later_rq() choose a closer cpu in topology Byungchul Park
2017-03-23 10:32 ` [PATCH 2/8] sched/deadline: Re-define parameters of cpudl heapify functions Byungchul Park
2017-03-23 10:32 ` [PATCH 3/8] sched/deadline: Add cpudl_maximum_dl() for clean-up Byungchul Park
2017-03-23 10:32 ` [PATCH 4/8] sched/deadline: Factor out the selecting of suitable max cpu Byungchul Park
2017-03-23 10:32 ` [PATCH 5/8] sched/deadline: Protect read of cpudl heap with a lock Byungchul Park
2017-03-23 10:32 ` [PATCH 6/8] sched/deadline: Don't return meaningless cpu in cpudl_maximum_cpu() Byungchul Park
2017-03-23 10:32 ` [PATCH 7/8] sched/deadline: Factor out the modifying of cpudl's heap tree Byungchul Park
2017-03-23 10:32 ` [PATCH 8/8] sched/deadline: Return the best satisfying affinity and dl in cpudl_find Byungchul Park
2017-03-23 22:36 ` Byungchul Park
2017-03-23 22:35 ` [PATCH 0/8] " Byungchul Park
2017-03-27 14:05 ` Juri Lelli [this message]
2017-03-28 0:42 ` Byungchul Park
2017-03-28 7:11 ` Juri Lelli
2017-03-28 7:29 ` Byungchul Park
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