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Date: Tue, 07 Jul 2026 10:56:06 -1000
Message-ID: <e18280314c02c349b186b09a3fef41af@kernel.org>
From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>,
 Changwoo Min <changwoo@igalia.com>,
 Joel Fernandes <joelagnelf@nvidia.com>,
 Emil Tsalapatis <emil@etsalapatis.com>,
 sched-ext@lists.linux.dev,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] sched_ext: Enable tick for finite slices on nohz_full
In-Reply-To: <20260707082537.918068-2-arighi@nvidia.com>
References: <20260707082537.918068-1-arighi@nvidia.com>
 <20260707082537.918068-2-arighi@nvidia.com>
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Hello, Andrea.

On Tue, Jul 07, 2026 at 10:17:59AM +0200, Andrea Righi wrote:
> 	if ((p->scx.slice == SCX_SLICE_INF) !=
> 	    (bool)(rq->scx.flags & SCX_RQ_CAN_STOP_TICK)) {
> 		if (p->scx.slice == SCX_SLICE_INF) {

The slice type is tested three times here (the XOR, the inner if, and the
finite tail). Can you split on it once instead?

	if (p->scx.slice == SCX_SLICE_INF) {
		if (!(rq->scx.flags & SCX_RQ_CAN_STOP_TICK)) {
			rq->scx.flags |= SCX_RQ_CAN_STOP_TICK;
			sched_update_tick_dependency(rq);
			update_other_load_avgs(rq);
		}
	} else {
		if (rq->scx.flags & SCX_RQ_CAN_STOP_TICK) {
			rq->scx.flags &= ~SCX_RQ_CAN_STOP_TICK;
			update_other_load_avgs(rq);
		}
		if (tick_nohz_full_cpu(cpu_of(rq)))
			tick_nohz_dep_set_cpu(cpu_of(rq), TICK_DEP_BIT_SCHED);
	}

update_other_load_avgs() lands in both arms, but the infinite/finite split
reads more directly than keying off the transition.

Thanks.

-- 
tejun