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 81650CD8CAD for ; Tue, 9 Jun 2026 07:28:30 +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-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GsYD70yDlULNNacQZMULeSKit2kKkOeG2bxsH2JA33s=; b=h6K/fg2FYZfTXO8SIhDD702IJz eW6zQfoNQNNsLfXVyBI1YiNzVElYHOSmtiL85Ah3ss7PSBJu2g/yHQVZO4/2SBjIxCl4nOC0bziv4 3ipIr9qSbCG3gbjVfGPG/16Ow43aAarsfQ5DUaUZMpzpdZP0GxIjKvZ231+lwntcBm+T+nojiMPPv wLKd7l4SS4SmbRIAUITGVG7rprlyEKKvj1nRQ1dSCTBmTTbRXi6fmm7tMVPxZWpJ/TL85rxEhijbg bVxX5JuK9g/VYdzEwTN+2QvETYwp2Ve9YXCQO3y9gHO8q+ciu5F2bPVefYxOLnwl59HhFKvpR1iki kyT4hoFw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wWqsu-00000004xtA-30dX; Tue, 09 Jun 2026 07:28:28 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wWqst-00000004xsx-3gM8; Tue, 09 Jun 2026 07:28:27 +0000 Date: Tue, 9 Jun 2026 00:28:27 -0700 From: Christoph Hellwig To: Hannes Reinecke Cc: lsf-pc , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , linux-mm@kvack.org Subject: Re: [LSF/MM/BPF TOPIC] Memory fragmentation with large block sizes Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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 Hannes, can you share your results on the mailing list? On Thu, Feb 19, 2026 at 10:54:48AM +0100, Hannes Reinecke wrote: > Hi all, > > I (together with the Czech Technical University) did some experiments trying > to measure memory fragmentation with large block sizes. > Testbed used was an nvme setup talking to a nvmet storage over > the network. > > Doing so raised some challenges: > > - How do you _generate_ memory fragmentation? The MM subsystem is > precisely geared up to avoid it, so you would need to come up > with some idea how to defeat it. With the help from Willy I managed > to come up with something, but I really would like to discuss > what would be the best option here. > - What is acceptable memory fragmentation? Are we good enough if the > measured fragmentation does not grow during the test runs? > - Do we have better visibility into memory fragmentation other than > just reading /proc/buddyinfo? > > And, of course, I would like to present (and discuss) the results > of the testruns done on 4k, 8k, and 16k blocksizes. > > Not sure if this should be a storage or MM topic; I'll let the > lsf-pc decide. > > Cheers, > > Hannes > -- > Dr. Hannes Reinecke Kernel Storage Architect > hare@suse.de +49 911 74053 688 > SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg > HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich > > ---end quoted text---