From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C227C3A5E6F; Sun, 18 Oct 2026 08:16:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792311362; cv=none; b=ZmZKVe/V+oHfvmoTwt/Hp6ajwns1JrHA4UFcYZHLd3FlMTwbbsSbpcVQoersmgcre19ZJrFIayB5ZpuWaDZejwQKUswYVNoJGalzViZe+psUg69dosoh+f7FTfvPU//k+AYHw9dkwWFUs7mrzAYL5S0UuVn6XkmDmkLPCsarDRM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792311362; c=relaxed/simple; bh=QuJRHnb2bQUlxOhxjd2d1R6J+j5fq43zPSPFaBVpYTk=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References; b=AZK/sPr1Wi8Agt9mXN6YVyIaL3pCzoE9f/wzLGfdqSOu1J5FWUeoLiLcYnkAILM3nscn5uIwBJYwPQJChwYqVDU8Wx1DpgrgL4JDJe7UCBOd1YJVg/V6S9/U/XdJTbdvskYpY8p0ClS41ZKUb34Uah3VfyNxr9cVUJWonPk7s20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Hjjd6ugx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Hjjd6ugx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 391BE1F000C5; Sun, 18 Oct 2026 08:16:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792311361; bh=QuJRHnb2bQUlxOhxjd2d1R6J+j5fq43zPSPFaBVpYTk=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=Hjjd6ugxnWecCNR8CB7E+pRf0/eMNOKFX8w7M/27XjsCBvMA+Vobi49xGS4tkmigd sQZb670OuYoBRdjPeSAkVbUTsFE9ca4o7S1fWKgGDbcYryxV+sInz2NZyqZnaQYt3B RNc+Zyp63QWWCeALqeWqtdxscOcoR8ogvSyEGqXrJfimkoCnWyxP6v/9Alh6jNi/SD R/iais4zpD9b5t7A+wPxvSrSSdUYiJCPmoZrM4AJiGwfVLxqWNaTmKq2i9uUrf3QMN aQZXLFdOa5LFJZVa6wO+wSGFMDyRNXA6ez2EkXTtsl3Se2eoDQvWeN02r5N3IhAk3o V9VcbP1IhEMxg== Date: Sat, 17 Oct 2026 22:16:00 -1000 Message-ID: From: Tejun Heo To: Andrea Righi Cc: sched-ext@lists.linux.dev, David Vernet , Changwoo Min , Emil Tsalapatis , David Dai , linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/6] sched_ext: Report the ecaps loss when a cpu goes offline In-Reply-To: References: <20261018015952.1499528-1-tj@kernel.org> <20261018015952.1499528-6-tj@kernel.org> Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Hello, Andrea. On Sun, Oct 18, 2026 at 09:01:18AM +0200, Andrea Righi wrote: > With a root-only scheduler the walk skips the root and queues nothing, but > resched_sync_ecaps() still runs on every online CPU, starting the ext_server and > queueing the resched irq work for no reason. Can we do it only if something was > actually queued? ... > ame on the offline side: with no sub-sched nr is 0, but we still do > update_rq_clock(), dl_server_start(&rq->ext_server) and the irq work on a CPU > that's going down and the ext_server stays enqueued there until > sched_cpu_dying() stops it. How about: These are on the cpu hotplug path, which is really cold, and the cost is a resched on one cpu. It's minuscule and doesn't matter, so I don't think it makes sense to add any complexity to avoid it. Thanks. -- tejun