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Wed, 13 Aug 2025 07:06:24 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFpv/Q7IKmuRFIHu+ImHkmhrZ82RJLQyLwegKcmcFgerq7rvJej1rqP6epJt+qtTMwfMXYXRg== X-Received: by 2002:a05:622a:1a23:b0:4ab:9586:bdd6 with SMTP id d75a77b69052e-4b0fc8cbeacmr46415431cf.53.1755093984373; Wed, 13 Aug 2025 07:06:24 -0700 (PDT) Received: from jlelli-thinkpadt14gen4.remote.csb ([2a02:b121:8f07:d6f6:1329:41fe:82dc:a703]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4b06787441fsm141781171cf.28.2025.08.13.07.06.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Aug 2025 07:06:23 -0700 (PDT) Date: Wed, 13 Aug 2025 16:06:15 +0200 From: Juri Lelli To: Yuri Andriaccio Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org, Luca Abeni , Yuri Andriaccio Subject: Re: [RFC PATCH v2 00/25] Hierarchical Constant Bandwidth Server Message-ID: References: <20250731105543.40832-1-yurand2000@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250731105543.40832-1-yurand2000@gmail.com> Hi, On 31/07/25 12:55, Yuri Andriaccio wrote: > Hello, > > This is the v2 for Hierarchical Constant Bandwidth Server, aiming at replacing > the current RT_GROUP_SCHED mechanism with something more robust and > theoretically sound. The patchset has been presented at OSPM25 > (https://retis.sssup.it/ospm-summit/), and a summary of its inner workings can > be found at https://lwn.net/Articles/1021332/ . You can find the v1 of this > patchset at the bottom of the page, which talks in more detail what this > patchset is all about and how it is implemented. > > The big update for this v2 version is the addition of migration code, which > allows to migrate tasks between different CPUs (following of course affinity > settings). > > As requested, we've split the big patches in smaller chunks in order to improve > in readability. Additionally, it has been rebased on the latest tip/master to > keep up with the latest scheduler updates and new features of dl_servers. > > Last but not least, the first patch, which has been presented separately at > https://lore.kernel.org/all/20250725164412.35912-1-yurand2000@gmail.com/ , is > necessary to fully utilize the deadline bandwidth while keeping the fair-servers > active. You can refer to the aforementioned link for details. The issue > presented in this patch also reflects in HCBS: in the current version of the > kernel, by default, 5% of the realtime bandwidth is reserved for fair-servers, > 5% is not usable, and only the remaining 90% could be used by deadline tasks, or > in our case, by HCBS dl_servers. The first patch addresses this issue and allows > to fully utilize the default 95% of bandwidth for rt-tasks/servers. > > Summary of the patches: > 1) Account fair-servers bw separately from other dl tasks and servers bw. > 2-5) Preparation patches, so that the RT classes' code can be used both > for normal and cgroup scheduling. > 6-15) Implementation of HCBS, no migration and only one level hierarchy. > The old RT_GROUP_SCHED code is removed. > 16-18) Remove cgroups v1 in favour of v2. > 19) Add support for deeper hierarchies. > 20-25) Add support for tasks migration. > > Updates from v1: > - Rebase to tip/master. Would you mind sharing the baseline sha this set applies to? It looks like it doesn't apply cleanly anymore. Thanks! Juri