From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 EA462C2FB for ; Mon, 7 Jul 2025 05:42:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751866956; cv=none; b=PqnPkpdAmJvbFOx4AKkulbMeapxwPaQDSaUyJSqPwubERzkWKUyFjUfgi7B/0jlHIR8kaK6/7CxZnPPBPGA2mYjExE3XbuSDBb/+H49GCLXPUsxwZo4didk5mQTBnqNWvZn/UdvM6D6lktCZCHEDoJ13asIIXZM4Nn42emODnYc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751866956; c=relaxed/simple; bh=kuw5IbnV7fi6rLoKY/KXvSEqEshcimO+A5gdlD8ZJyM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gcACazluDlHLkZ/qbycavwkPBSxPyp+uhbPFZHEy8niWQw1b8Rk2ydLro5GEtDJ6rGE4CbKKgS854dm//ga3WRI6kFDEAn1ZcOSQQWDfgWjKKMBwccRbs6HgEewi/sgJ9lbzQne0Eg+F6Pl7OnQME+jp28uEWWUBEYbzDuobXMw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 07766227A87; Mon, 7 Jul 2025 07:42:28 +0200 (CEST) Date: Mon, 7 Jul 2025 07:42:27 +0200 From: Christoph Hellwig To: Daniel Wagner Cc: Christoph Hellwig , Daniel Wagner , Jens Axboe , Keith Busch , Sagi Grimberg , "Michael S. Tsirkin" , Aaron Tomlin , "Martin K. Petersen" , Thomas Gleixner , Costa Shulyupin , Juri Lelli , Valentin Schneider , Waiman Long , Ming Lei , Frederic Weisbecker , Mel Gorman , Hannes Reinecke , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, megaraidlinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, storagedev@microchip.com, virtualization@lists.linux.dev, GR-QLogic-Storage-Upstream@marvell.com Subject: Re: [PATCH v7 08/10] blk-mq: use hk cpus only when isolcpus=io_queue is enabled Message-ID: <20250707054227.GB28625@lst.de> References: <20250702-isolcpus-io-queues-v7-0-557aa7eacce4@kernel.org> <20250702-isolcpus-io-queues-v7-8-557aa7eacce4@kernel.org> <20250703090158.GA4757@lst.de> <75aafd33-0aff-4cf7-872f-f110ed896213@flourine.local> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75aafd33-0aff-4cf7-872f-f110ed896213@flourine.local> User-Agent: Mutt/1.5.17 (2007-11-01) On Fri, Jul 04, 2025 at 11:00:56AM +0200, Daniel Wagner wrote: > > I'm no expert on the housekeeping stuff, but why isn't the > > housekeeping_enabled check done in housekeeping_cpumask directly so > > that the drivers could use housekeeping_cpumask without a blk-mq > > wrapper? > > Yes, housekeeping_cpumask will return cpu_possible_mask when housekeping > is disabled. Though some drivers want cpu_online_mask instead. If all > drivers would agree on one version of the mask it should allow to drop > to these helpers (maybe we the houskeeping API needs to be extended then > though) Drivers don't get cpu hotplug notifications, so cpu_possible_mask is the only valid answer right now. That could change if we ever implement notifications to the drivers. > This is also what Hannes brought up. If the number of supported hardware > queues for a device is less than cpu_possible_mask, it really makes > sense to distribute the hardware queues only between the online cpus. I > think the only two drivers which are interested in the cpu_possible_mask > are nvme-pci and virtio. That's the only two drivers that get it right :(