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([2a09:bac1:2880:f0::3d8:2f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439dae45786sm41385272f8f.32.2026.03.10.07.52.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 07:52:14 -0700 (PDT) From: Matt Fleming To: sched-ext@lists.linux.dev Cc: kernel-team@cloudflare.com, tj@kernel.org, arighi@nvidia.com, void@manifault.com, changwoo@igalia.com, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: sched_ext: Partial mode priority and fallthrough to EEVDF Date: Tue, 10 Mar 2026 14:52:13 +0000 Message-ID: <20260310145213.1060649-1-matt@readmodwrite.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, At Cloudflare we're experimenting with inverting the priority of the ext_sched_class and fair_sched_class to allow us to pick SCHED_EXT tasks to run before SCHED_NORMAL. This gives us better scheduling decisions for those SCHED_EXT tasks where we can embed business logic into the BPF program and prevents them being starved by the larger number of SCHED_NORMAL tasks under CPU contention. There are a couple of reasons we took this route: 1. Our workloads are heterogeneous and complex and we can't move entire systems to SCHED_EXT in one shot. We want to experiment with running SCHED_EXT in partial mode as we progressively onboard more and more services (we run multiple services on single machines). 2. There's no way today (AFAIK) to run in "full-mode" and have BPF schedulers fallthrough to EEVDF. In an ideal world, 2 is what we'd want to do. Is anyone else interested in this problem or currently working on it? Is there anything coming in the future that would make it easier for those of us slowly transitioning to SCHED_EXT? Thanks, Matt