Date: Fri, 24 Mar 2017 07:35:02 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: <peterz@infradead.org>, <mingo@kernel.org>
CC: <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
Message-ID: <20170323223502.GR11100@X58A-UD3R>
References: <1490265163-29981-1-git-send-email-byungchul.park@lge.com>
MIME-Version: 1.0
In-Reply-To: <1490265163-29981-1-git-send-email-byungchul.park@lge.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1957
Lines: 44

On Thu, Mar 23, 2017 at 07:32:35PM +0900, 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).
                                  ^
                              should be 1
> 
>    where cpu 3 want to push a task (affinity is 1 2 3 and dl is 1).
                                                                  ^
                                                        should be 2
> 
> 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.
> 
> Byungchul Park (8):
>   sched/deadline: Make find_later_rq() choose a closer cpu in topology
>   sched/deadline: Re-define parameters of cpudl heapify functions
>   sched/deadline: Add cpudl_maximum_dl() for clean-up
>   sched/deadline: Factor out the selecting of suitable max cpu
>   sched/deadline: Protect read of cpudl heap with a lock
>   sched/deadline: Don't return meaningless cpu in cpudl_maximum_cpu()
>   sched/deadline: Factor out the modifying of cpudl's heap tree
>   sched/deadline: Return the best satisfying affinity and dl in
>     cpudl_find
> 
>  kernel/sched/cpudeadline.c | 228 +++++++++++++++++++++++++++++++--------------
>  kernel/sched/cpudeadline.h |   9 ++
>  kernel/sched/deadline.c    |  29 +++---
>  3 files changed, 182 insertions(+), 84 deletions(-)
> 
> -- 
> 1.9.1