Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <eda74c03-bde2-bb51-2b0d-df2097215696@redhat.com>
Date:   Tue, 18 Apr 2023 10:31:27 -0400
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: [PATCH 0/6] sched/deadline: cpuset: Rework DEADLINE bandwidth
 restoration
Content-Language: en-US
To:     Qais Yousef <qyousef@layalina.io>,
        Juri Lelli <juri.lelli@redhat.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, Tejun Heo <tj@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Hao Luo <haoluo@google.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it,
        claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it,
        bristot@redhat.com, mathieu.poirier@linaro.org,
        cgroups@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Wei Wang <wvw@google.com>, Rick Yiu <rickyiu@google.com>,
        Quentin Perret <qperret@google.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Sudeep Holla <sudeep.holla@arm.com>
References: <20230329125558.255239-1-juri.lelli@redhat.com>
 <20230418141127.zbvsf7lwk27zvipt@airbuntu>
From:   Waiman Long <longman@redhat.com>
In-Reply-To: <20230418141127.zbvsf7lwk27zvipt@airbuntu>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 4/18/23 10:11, Qais Yousef wrote:
> On 03/29/23 14:55, Juri Lelli wrote:
>> Qais reported [1] that iterating over all tasks when rebuilding root
>> domains for finding out which ones are DEADLINE and need their bandwidth
>> correctly restored on such root domains can be a costly operation (10+
>> ms delays on suspend-resume). He proposed we skip rebuilding root
>> domains for certain operations, but that approach seemed arch specific
>> and possibly prone to errors, as paths that ultimately trigger a rebuild
>> might be quite convoluted (thanks Qais for spending time on this!).
>>
>> To fix the problem
>>
>>   01/06 - Rename functions deadline with DEADLINE accounting (cleanup
>>           suggested by Qais) - no functional change
>>   02/06 - Bring back cpuset_mutex (so that we have write access to cpusets
>>           from scheduler operations - and we also fix some problems
>>           associated to percpu_cpuset_rwsem)
>>   03/06 - Keep track of the number of DEADLINE tasks belonging to each cpuset
>>   04/06 - Create DL BW alloc, free & check overflow interface for bulk
>>           bandwidth allocation/removal - no functional change
>>   05/06 - Fix bandwidth allocation handling for cgroup operation
>>           involving multiple tasks
>>   06/06 - Use this information to only perform the costly iteration if
>>           DEADLINE tasks are actually present in the cpuset for which a
>>           corresponding root domain is being rebuilt
>>
>> With respect to the RFC posting [2]
>>
>>   1 - rename DEADLINE bandwidth accounting functions - Qais
>>   2 - call inc/dec_dl_tasks_cs from switched_{to,from}_dl - Qais
>>   3 - fix DEADLINE bandwidth allocation with multiple tasks - Waiman,
>>       contributed by Dietmar
>>
>> This set is also available from
>>
>> https://github.com/jlelli/linux.git deadline/rework-cpusets
> Is this just waiting to be picked up or still there's something to be addressed
> still?

There are some changes to cpuset code recently and so I believe that 
this patch series may need to be refreshed to reconcile the changes.

Thanks,
Longman