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[2.102.14.151]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-7077ca2ee44sm60159476d6.29.2025.08.04.09.58.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Aug 2025 09:58:58 -0700 (PDT) Date: Mon, 4 Aug 2025 17:58:55 +0100 From: Juri Lelli To: David Haufe Cc: linux-kernel@vger.kernel.org Subject: Re: Kernel 6.14.11 dl_server_timer(...) causing IPI/Function Call Interrupts on isolcpu/nohz_full cores, performance regression Message-ID: References: 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: On 04/08/25 10:44, David Haufe wrote: > My apologies, I see what you mean now. add_nr_running() is not being > invoked if it is the dl_server. We are still trying to get this branch > to boot to verify ourselves. We will be on the lookout for this to be > merged for release. No worries, guess I wasn't clear the first time. :) I added a very much experimental commit on https://github.com/jlelli/linux/tree/upstream/fix-dlserver-1 that seems to be able to remove the one per second dl_server_timer and start it back as needed. But, I just played briefly with it, so I am not fully convinced is what we want. Anyway, if you could test with it as well it would be a useful data point. In principle you could try porting the following commits to your current tree and check if they do improve things (in reverse order starting from the bottom from the branch above): f237e524f3c7 ("sched/deadline: Make dl-server nohz full aware") 219a63335b67 ("sched/deadline: Don't count nr_running twice for dl_server proxy tasks") 7620177e8108 ("sched/deadline: Fix RT task potential starvation when expiry time passed") cccb45d7c429 ("sched/deadline: Less agressive dl_server handling") Thanks! Juri