From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 344FA2D5925 for ; Tue, 9 Jun 2026 11:25:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781004325; cv=none; b=oGHVW65p7luwx12gTbGd/WNEbqj1exdqQtLwG5/L3nd4FX0VB69QZzh7hyF7qNDc5VuS0anLvutHw7mN3Pa7v03sQPnXg0Gza8yY3d09LqGQhTr0l6U0uR1Cqs7tTN/Lj/HIPc8exf0JHUq099z2SvwYXTBXsWh1Wqq0/6gglCg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781004325; c=relaxed/simple; bh=RpCa7hSz4QIstAIaOK/qT1vkMlq4XJqSGlGJyGk0tm4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=A8D+I5YZuUWWc9B9r9UKwLP2+CJoQKlkrHnjp/3nGkM1p5OrO3j47ZzIbU4tvC33yqGQ+BLVZXzZwTtrQ4fcKDDIhAkAp0xTOqtyW+5drz4xTL2IL6A5RWT24X7N3Jp7DDLPXZIPiU9FLyrRJ9jQaGPqXB0n9Hxwp6meUM4NwPc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=R7gXTqCb; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="R7gXTqCb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Qf+SVKWwcSjN2XY9tUh6MjBGq3HpyBf4my+a9eDjfYY=; b=R7gXTqCbB4VkRjDzca7ehmqafW KiENjlfCTKPFSPRVDm2P46pN/UhdwRJ8VoDdetASNITj6EBCjqn71/p6TofYOWQ49PylTkRNUMtS3 Tvn8JTkg0YjrM++5w4xmCbNzvbGS+czdQKyIHPfk5VfWvLT7CR3OwNRUzVFdACP7K+nFS2wA1g6dA UKTecwBKkSdEJYDu9VzaKX6w649Uc7SGqNlr323I4wB4Jlc6hEZxdkpXsWQaYAONYkk5f42IxcTYj 1jSQk350qc1o/5JX74xQoY6UeVuaCtCk/7LhjzOWFMx2gmDPgeTHnPSQvRBF02fxb4rRdWl5RwikP u30L/mTw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1wWuZv-00000002Nc2-10fQ; Tue, 09 Jun 2026 11:25:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 0BFC5302F12; Tue, 09 Jun 2026 13:25:05 +0200 (CEST) Date: Tue, 9 Jun 2026 13:25:05 +0200 From: Peter Zijlstra To: Shrikanth Hegde Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com, kprateek.nayak@amd.com, iii@linux.ibm.com, tglx@kernel.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, mgorman@suse.de, bsegall@google.com, maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com, chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org, arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com, tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org, rafael@kernel.org Subject: Re: [PATCH v3 09/20] sched/rt: Select a preferred CPU for wakeup and pulling rt task Message-ID: <20260609112505.GC48970@noisy.programming.kicks-ass.net> References: <20260514152204.481115-1-sshegde@linux.ibm.com> <20260514152204.481115-10-sshegde@linux.ibm.com> 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: <20260514152204.481115-10-sshegde@linux.ibm.com> On Thu, May 14, 2026 at 08:51:53PM +0530, Shrikanth Hegde wrote: > For RT class, > - During wakeup choose a preferred CPU. > - For push_rt framework, limit pushing to preferred CPUs > - Pull the rt task only if CPU is preferred. So this one might have the potential to break things. Preferring a preferred cpu, sure, but to the exclusion of active, perhaps not. Also, where are the DL changes? > Signed-off-by: Shrikanth Hegde > --- > kernel/sched/cpupri.c | 1 + > kernel/sched/rt.c | 4 ++++ > 2 files changed, 5 insertions(+) > > diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c > index 8f2237e8b484..24eb26ea9a91 100644 > --- a/kernel/sched/cpupri.c > +++ b/kernel/sched/cpupri.c > @@ -103,6 +103,7 @@ static inline int __cpupri_find(struct cpupri *cp, struct task_struct *p, > if (lowest_mask) { > cpumask_and(lowest_mask, &p->cpus_mask, vec->mask); > cpumask_and(lowest_mask, lowest_mask, cpu_active_mask); > + cpumask_and(lowest_mask, lowest_mask, cpu_preferred_mask); > > /* > * We have to ensure that we have at least one bit > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 4ee8faf01441..62c53f10de24 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -2262,6 +2262,10 @@ static void pull_rt_task(struct rq *this_rq) > if (likely(!rt_overload_count)) > return; > > + /* No point in pulling the load, just to push it next tick again */ > + if (!cpu_preferred(this_cpu)) > + return; > + > /* > * Match the barrier from rt_set_overloaded; this guarantees that if we > * see overloaded we must also see the rto_mask bit. > -- > 2.47.3 >