From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7B6481D7984; Sat, 13 Sep 2025 22:32:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757802749; cv=none; b=jtwZdZ+sSw+7cSZXBdgAX3farg82V9nZn4w24REJFZcuYrp07+OtczSqfBFbfM0f5EE2Rx89+TvbynvGmbf1zSTB0Pjw7VW23R8EF+6oP6U/JvIxO8QzAUFW4gfwNh6qeExLM7vuWjcXcAhh4Fwc1cgZUnFvzzTyjvawH3DrcNU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757802749; c=relaxed/simple; bh=+cx1XGB5AUqRTT31YlcTyMc4JGYSAoJbSnKDP8tEAu8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PN+TQFTITC8vbzEFkey+0+Dajviro+ePlS+dPjwzA5/6s78F2Ign18Lwl2deS/AM2gwGgiGRKdDEN155+lEQv9QliF35Pkc1G7aTPDrq07YUrOhXmvn2XRF6dcQKtP/2y4erPNYpJjNFKDsUcwbtv6kKK9jx8gioxMFWPa3LauQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s06s7Cdc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="s06s7Cdc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBE1FC4CEEB; Sat, 13 Sep 2025 22:32:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757802749; bh=+cx1XGB5AUqRTT31YlcTyMc4JGYSAoJbSnKDP8tEAu8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s06s7CdcaszdHuwxPqGiSsBxOluZLuB1g8e04OmqX1Ip99TmI8xwE8O+/+Fw/oAIM w0klN7r5vjBZxTAWPTSS8HfoioXin74uMgrDfHsovLYJ7GVNy/Kk0sTXcpRJ0ebkJ0 y6YRWNBx3DgFdd6EDAlZwJOUE4BlkYcl4kTZYqi4mgMvwTjljtfmVEjs0gltvMSk2U yH4QszBzqC8dUhV9u+lqMY4H/d8XX+a6MhtXwsC5t/Ez/f3ZwtumzM+mM+GFw9Uafv ubGqqPSSQeXAckfPhYdQffmhMxegMGSipMNqiGWEEZ4yoVZRvi8+ZtvTycMal/yqIo oQe6kde9hO9hw== Date: Sat, 13 Sep 2025 12:32:27 -1000 From: Tejun Heo To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, longman@redhat.com, hannes@cmpxchg.org, mkoutny@suse.com, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, cgroups@vger.kernel.org, sched-ext@lists.linux.dev, liuwenfang@honor.com, tglx@linutronix.de Subject: Re: [PATCH 13/14] sched: Add {DE,EN}QUEUE_LOCKED Message-ID: References: <20250910154409.446470175@infradead.org> <20250910155809.800554594@infradead.org> <20250911094240.GW3289052@noisy.programming.kicks-ass.net> <20250912141904.GA3289052@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: cgroups@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: Hello, On Fri, Sep 12, 2025 at 06:32:32AM -1000, Tejun Heo wrote: > Yeah, or I can make scx_tasks iteration smarter so that it can skip through > the list for tasks which aren't runnable. As long as it doesn't do lock ops > on every task, it should be fine. I think this is solvable one way or > another. Let's continue in the other subthread. Thought more about it. There's another use case for this runnable list, which is the watchdog. As in the migration synchronization, I think the right thing to do here is just adding a nested lock. That doesn't add any overhead or complications to other sched classes and from sched_ext POV given how expensive migrations can be, if we make that a bit cheaper (and I believe we will with changes being discussed), added up, the outcome would likely be lower overhead. Thanks. -- tejun