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Tue, 11 Nov 2025 06:57:48 -0800 (PST) Date: Tue, 11 Nov 2025 09:57:46 -0500 From: Dan Schatzberg To: Tejun Heo Cc: David Vernet , Andrea Righi , Changwoo Min , Emil Tsalapatis , sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/13] sched_ext: Make slice values tunable and use shorter slice in bypass mode Message-ID: References: <20251109183112.2412147-1-tj@kernel.org> <20251109183112.2412147-3-tj@kernel.org> 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: <20251109183112.2412147-3-tj@kernel.org> On Sun, Nov 09, 2025 at 08:31:01AM -1000, Tejun Heo wrote: > @@ -919,7 +948,7 @@ static void dsq_mod_nr(struct scx_dispatch_q *dsq, s32 delta) > > static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p) > { > - p->scx.slice = SCX_SLICE_DFL; > + p->scx.slice = scx_slice_dfl; Do you need to use READ_ONCE here given that this can be modified concurrently? > __scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1); > } > > @@ -2892,7 +2921,7 @@ void init_scx_entity(struct sched_ext_entity *scx) > INIT_LIST_HEAD(&scx->runnable_node); > scx->runnable_at = jiffies; > scx->ddsp_dsq_id = SCX_DSQ_INVALID; > - scx->slice = SCX_SLICE_DFL; > + scx->slice = scx_slice_dfl; > } > > void scx_pre_fork(struct task_struct *p) > @@ -3770,6 +3799,7 @@ static void scx_bypass(bool bypass) > WARN_ON_ONCE(scx_bypass_depth <= 0); > if (scx_bypass_depth != 1) > goto unlock; > + scx_slice_dfl = scx_slice_bypass_us * NSEC_PER_USEC; Similarly WRITE_ONCE here > bypass_timestamp = ktime_get_ns(); > if (sch) > scx_add_event(sch, SCX_EV_BYPASS_ACTIVATE, 1); > @@ -3778,6 +3808,7 @@ static void scx_bypass(bool bypass) > WARN_ON_ONCE(scx_bypass_depth < 0); > if (scx_bypass_depth != 0) > goto unlock; > + scx_slice_dfl = scx_slice_dfl_us * NSEC_PER_USEC; And here > if (sch) > scx_add_event(sch, SCX_EV_BYPASS_DURATION, > ktime_get_ns() - bypass_timestamp); > @@ -4776,7 +4807,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) > queue_flags |= DEQUEUE_CLASS; > > scoped_guard (sched_change, p, queue_flags) { > - p->scx.slice = SCX_SLICE_DFL; > + p->scx.slice = scx_slice_dfl; And here > p->sched_class = new_class; > } > } > -- > 2.51.1 >