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Thu, 06 Nov 2025 22:51:52 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.129.40]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42abe63dfecsm3408533f8f.12.2025.11.06.22.51.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Nov 2025 22:51:51 -0800 (PST) Date: Fri, 7 Nov 2025 07:51:49 +0100 From: Juri Lelli To: Andrea Righi Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tejun Heo , David Vernet , Changwoo Min , Shuah Khan , Joel Fernandes , Christian Loehle , Emil Tsalapatis , Luigi De Matteis , sched-ext@lists.linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/11] sched/debug: Stop and start server based on if it was active Message-ID: References: <20251029191111.167537-1-arighi@nvidia.com> <20251029191111.167537-3-arighi@nvidia.com> Precedence: bulk X-Mailing-List: linux-kselftest@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 06/11/25 17:39, Andrea Righi wrote: > On Thu, Nov 06, 2025 at 08:13:39AM +0100, Juri Lelli wrote: ... > > > @@ -376,8 +378,11 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu > > > return -EINVAL; > > > } > > > > > > - update_rq_clock(rq); > > > - dl_server_stop(&rq->fair_server); > > > + is_active = dl_server_active(&rq->fair_server); > > > + if (is_active) { > > > + update_rq_clock(rq); > > > + dl_server_stop(&rq->fair_server); > > > + } > > > > > > retval = dl_server_apply_params(&rq->fair_server, runtime, period, 0); > > > > > > @@ -385,7 +390,7 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu > > > printk_deferred("Fair server disabled in CPU %d, system may crash due to starvation.\n", > > > cpu_of(rq)); > > > > > > - if (rq->cfs.h_nr_queued) > > > + if (is_active) > > > dl_server_start(&rq->fair_server); > > > > Something that I noticed while reviewing this series is that we still > > start back a server even if the user put its runtime to zero (disabling > > it) and I don't think we want to do that. It's not of course related to > > this change or this series per-se, but something we probably want to fix > > independently. > > Should we just call dl_server_remove_params() when runtime is zero? Looking again at it I actually wonder if wouldn't it be better to use dl_server_apply_params(dl_se, 0, dl_se->dl_period, false) in both cases. dl_rq_change_utilization() deals with dl_non_contending (inactive_timer armed) case already (even though sub-optimally, but we can fix/change it later), so we can probably remove the special handling you do in dl_server_remove_params(). The WARN_ON_ONCE(on_dl_rq()) could be moved to dl_server_apply_params() as well. What do you think?