From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C7DFCCED61E for ; Wed, 9 Oct 2024 08:03:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=axFQRrF2Y8HkeQ4+fO7T8+Nt4YU1FpmE7EWBJtnvsvg=; b=FNYxOgz7V5YHE9ntvU9OhxguqY 0DuGTynfHaTsaGmr6RJLJKgCfQ1TVtpduAQ49zAKulHMAxxmsZFAVthmG5QTMtnKjIGAQ8Y6b5V9j YHeDXrTDwnjTjCqccG2UP25Qm6CD2aWXQojtSK5oQb5um8JUqk09U4dBtpsMC238ZjiC/BSea+ac3 FncfTaXPj0/dCobgFzHW837XEvrF8xAeFzxQb8TIvir/+ssF4IWVBiWyUzoaqjlnXo61SgqeBmxr5 VLbXDeHEeTTKCwUeO1kugQsWb9j6R/PpfS51wzvM9yHZ4Sj3x1Z9peD915cXYYoA4MeEHKNDjYtOJ EccYz7Kg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1syRfi-00000008MY2-1Eil; Wed, 09 Oct 2024 08:03:50 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1syRct-00000008Lzo-3SGh for linux-nvme@lists.infradead.org; Wed, 09 Oct 2024 08:00:57 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 2FF24227A8E; Wed, 9 Oct 2024 10:00:52 +0200 (CEST) Date: Wed, 9 Oct 2024 10:00:52 +0200 From: Christoph Hellwig To: Tero Kristo Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, axboe@kernel.dk, linux-nvme@lists.infradead.org, sagi@grimberg.me, kbusch@kernel.org Subject: Re: [PATCH 1/1] nvme-pci: Add CPU latency pm-qos handling Message-ID: <20241009080052.GA16711@lst.de> References: <20241004101014.3716006-1-tero.kristo@linux.intel.com> <20241004101014.3716006-2-tero.kristo@linux.intel.com> <20241007061926.GA800@lst.de> <913b063d0638614bc95d92969879d2096ffc0722.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <913b063d0638614bc95d92969879d2096ffc0722.camel@linux.intel.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241009_010056_028029_FA196501 X-CRM114-Status: GOOD ( 13.99 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, Oct 09, 2024 at 09:45:07AM +0300, Tero Kristo wrote: > Initially, I posted the patch against block layer, but there the > recommendation was to move this closer to the HW; i.e. NVMe driver > level. Even if it is called from NVMe, at lot of the code is not nvme specific. Some of it appears block specific and other pats are entirely generic. But I still don't see how walking cpumasks and updating paramters in far away (in terms of cache lines and pointer dereferences) for every single I/O could work without having a huge performance impact.