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([2601:188:ca00:a00:f844:fad5:7984:7bd7]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d40dbe1491sm224006d6.2.2024.11.15.11.39.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Nov 2024 11:39:27 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <896fe0bd-41a1-4613-a3f7-f3ccf80d880c@redhat.com> Date: Fri, 15 Nov 2024 14:39:26 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] sched/isolation: Exclude dynamically isolated CPUs from housekeeping masks To: =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: Tejun Heo , Johannes Weiner , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Frederic Weisbecker , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Costa Shulyupin , Daniel Wagner References: Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/15/24 2:32 PM, Waiman Long wrote: > On 11/15/24 10:45 AM, Michal Koutný wrote: >> Hello. >> >> I recently liked the idea of considering isolated CPUs a static (boot >> time) resource and only use cpusets to place (or remove) sensitive >> workload from those selected CPUs depending on current needs. (Yes, this >> may not efficiently utilize the isolated CPUs when reserve them based on >> maximum needs of a node.) > > Thanks for taking a look at this. > > Yes, I am moving in this direction too. Boot time statically isolated > CPUs have better isolation than is currently possible if we do it > dynamically at run time, though we are trying to close the gap. > >> >> >> On Wed, Aug 21, 2024 at 10:23:11AM GMT, Waiman Long >> wrote: >>> This patch is a step in that direction by making the housekeeping CPU >>> mask APIs exclude the dynamically isolated CPUs when they are called >>> at run time. The housekeeping CPU masks will fall back to the bootup >>> default when all the dynamically isolated CPUs are released. >> But when I look at it with the dynamism in mind, I would expect that >> some API like housekeeping_setup_type(), i.e. modify the set of isolated >> CPUs are requested and leave it up to the isolation implementation to >> propagate any changes to respective subsystems. And return an error of >> type contains a flag for which dynamism isn't implemented yet or not >> possible. > > There are currently 9 different hk_type's defined in > include/linux/sched/isolation.h. We are now trying to reduce their > number as some of them cannot be set independently. See [1]. I am > thinking about doing dynamism in the best effort basis. Of course, we > could expose some information about what aspect of dynamic isolation > can be enabled at the moment, if necessary. Forgot to put the link. [1] https://lore.kernel.org/lkml/20240921190720.106195-1-longman@redhat.com/ > > Cheers, > Longman >