From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f43.google.com (mail-wr1-f43.google.com [209.85.221.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4729226FD9B for ; Wed, 10 Jun 2026 22:27:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781130436; cv=none; b=bc5j96htL9NOFtxTc2duIAfCjdHOGRZqDQkMf3kVaevcabTKeAdUXPfg4M7HAzlVttJPVoFvSDlzaH+iS6Aj8zLCtPmWPRHcQ88gm36e1cEqjA6hgKG+7zNPzSRn0GIMXMuO+HA8ydEQ4F3g+DYjRhSx2C9b8dvmQpmya+eYSKY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781130436; c=relaxed/simple; bh=1cQ/0cWbfEBqHI5r0H10tWo99TR+KBIClcsmuqhCU2o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LlbkNFr4hvSKZNfGrgKLbBZpKfqueqz/l9DgkYxlZhvGaYcvNGeBCBlcEUN7XdJf8Wv/TvYTZnxfI5n1RJWLVbTg6n3xd+gQAyo/zdXyi+XviZr1JkacOXOwXKpP6ZaNb9ldzkFqYYJuJ+woOYufrIh/F4DFbmEUTiC+Kxnycas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Ul/h5e1v; arc=none smtp.client-ip=209.85.221.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ul/h5e1v" Received: by mail-wr1-f43.google.com with SMTP id ffacd0b85a97d-45ee5cdbd28so179927f8f.1 for ; Wed, 10 Jun 2026 15:27:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1781130434; x=1781735234; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=ERJnitgYeN+oHp0QIhM2Gx0sT2CNtRoOhhriDExY+yw=; b=Ul/h5e1vpBOCb3nE7pvmbf5uxlRGzQM+y8jdIEYplelFlyJqriZyrljmpVEh4cumDf SxI/CTHNXM2fmP4SCcCc6pL6QTvjB1SNmubNn3pRalH9FZ2ymRmJypwbY0cizHWjNoGa 6DO3cU06By59KmwdXxpfBdHowyKrY6ooRNm876jacdOeHx9VXiszNYzJ6VRoAJhiABPl FvIBy7Lw3nv7CFdKKFkkRDrIfliBJFiE8Q+uykwDULTCw+HCCJw16KgJ3XMWAOrr9pHW SeQb9MfdF20VW1YCRF2pwJpTmGKe2niIP0K8ciQE9M2btmTQ5WTY5GlNZnTqDS/BHZq7 xygg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781130434; x=1781735234; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ERJnitgYeN+oHp0QIhM2Gx0sT2CNtRoOhhriDExY+yw=; b=P+cswrz5MfApK1Gl89gKXhhxNMzVQBJa8VqZWosBIS4IUm7VKZUlwe5qrEoF/1noAo FmA0Hknsp0SrKaIb5rMzZqvb3G7N41MGkwUOIq8U2nDEJzrnf95x57Dvbn/0gUiH3cof jkG3H01losf6gFVoQviZleb0dr9XP1lCYunqdgXQWr2uSb7jJpoNYrIv6VPT9WnXO8cg sIJDY0sUf8Eq142AwveSE5kYbAFIWFPKGYXyx41h5LlyCEiCAciyOC5Q8U7nhGmOfXrc t5VgUNFY4MnotP6hE6Y1/KgAniMwBdP96mDfOViruBkCeE5rEZQ2vS7oIzlWMjpoe9DQ hXDg== X-Forwarded-Encrypted: i=1; AFNElJ++MazIxGc997LKdrJpLn3vy9rSTRev/b78xoXJPFx52/HB/T4KiIeN4i32HlDfhcUG5FSiYBW9kZHotQ==@vger.kernel.org X-Gm-Message-State: AOJu0Yw71fumQVIK+k43za/xPywQFp5gTrwKVoxWzSvb2K/doJes78TD jbA3v7Pn3xoWYAD1kkGCCubyz67XMwnvjl3+8su0vMplAlIZm4eahppd X-Gm-Gg: Acq92OHPNCHCZIrVmFhXT6jcfTAYM5kzOG5WlBi9y/vnFCXLpRiq10UvGk6MJG6By2F E25pTGuQhczJov2rQTIG1GOHHYQz+cho818E6aHuvYI2Zlq5X7ATyJm9kozpLptGYcdMiTno1aE tSUz5mRk/TKVu+MjfHjZ56fcPo8lkDtp4iEGGb4Pez2D2EqZg0YmIV0vfLyEYHOyN00752PmPT5 LfDg7rHaL99qA4SdZRvTDa/f1RUJWlhy5sTJIrXcyEebVDl/OU3wwSSO4KE5TyQeNQGhv6B7Prg +mzPsP4YLdVxYcTzE+5zyYYVhj+CoAoIBE+pMLrECdw/TtU7SDHQBv8h7EEsDDwBtJ4+YA9sZhk k4vderSc90uycTtVm8UsVydMGz8jr3MHNhUyt9TypT5wNB7uPQrFnnE+VQq43KOwxJFBRxTQBZK t8EJ2hJ9sLE5Q5tvfM20xd81AQFwuCrrNkHEiOcc0/tQBp1AegB/RQ8YLMNy5VNkhqluSrhtnWR nrSPZHxcAyRgcgEjR2A7Djz52Y0rE3m5rCPuZq5tDE/ow== X-Received: by 2002:a05:6000:461a:b0:460:d18:865c with SMTP id ffacd0b85a97d-460664c54bbmr512993f8f.1.1781130433530; Wed, 10 Jun 2026 15:27:13 -0700 (PDT) Received: from localhost (pat-125-253.wlan.net.ed.ac.uk. [192.41.125.253]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f2dcae2sm80574537f8f.6.2026.06.10.15.27.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jun 2026 15:27:12 -0700 (PDT) Date: Wed, 10 Jun 2026 23:27:12 +0100 From: Karim Manaouil 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: <20260610222712.cmbforeivf7h544y@wrangler> References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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. thpchallenge from mmtests has been a staple for the compaction/anti fragmentation folks. And check this https://patchwork.freedesktop.org/patch/716404/?series=164353&rev=1 Btw, do you mind sharing what workloads you discussed with Matthew? > - 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 > -- ~karim