From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 003.mia.mailroute.net (003.mia.mailroute.net [199.89.3.6]) (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 8653C10F9; Mon, 24 Mar 2025 10:58:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.3.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742813931; cv=none; b=LUsIuuUXv15I7Fwe0YJQBW8aM1n9uPpaWXcKlyBnOE5LVDbUfuAHBBImsSrRXYpmqXZ9JOwJ9RKl8Q+rgrjGp1vfESdjPzTRwpIu7GMwQyeM0HUEjsePaPx21fymakadhpURNgnSpmN6uzXRIKP5Kex9zBbJn2/A7C90CrILFA8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742813931; c=relaxed/simple; bh=4yVXdodDIfdUdrQgYWR7r1IWVSW9cP+OijHo91EXgFE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PKmKd5WxTSd/QgDIjOSqSGFKiXNqvY0UFAEq/EGapSBMHIScv6ivUu8H4EVQRTnKJdhpfNHo4j4SIX8ywHJ3Wo5ba2aoNktVppcYfExuhKPL9qkoCRBBsC4g52Cevikifi17HR7djV4XZW6nC4IJ90qXiAU0BMYMh15RCT+Nni4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=weSd2VmF; arc=none smtp.client-ip=199.89.3.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="weSd2VmF" Received: from localhost (localhost [127.0.0.1]) by 003.mia.mailroute.net (Postfix) with ESMTP id 4ZLqmS1qwtzm0R3r; Mon, 24 Mar 2025 10:58:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1742813925; x=1745405926; bh=qHWnXl7QzKO/pXeMQIokr+0r ghD0nnpt18hbCu3fEWw=; b=weSd2VmF2OMTqgTjsbIuZtT/MRyOanBpLKlCYj7Y RECtUB+Sy5QO2wOxdv3LKADHEGtWXwKh9BgTTcIdEPWpmq1hnjgaVYglOlMuEiHM rglZrP3CiALvb8X6xbDD5JP79/PEJy+FJBe48GnZD1OUviyCzJS/PZ/mM+njGDZN wyGOu5/MXIoVAJq6CwUoMhcnSDqKaJikeS6tIDLrSoYyH/LXYvx1voganLX+kicj s1HLfdYTI0f/Ad0TTSbExUfHlxa2hYLVK96RxJFZfAezOkLM9777is2jiVjJu0Aj leJOwJNiSqlPs8lOTj4CEj2fZ7SgWdv6wBvYk/OjbipFyw== X-Virus-Scanned: by MailRoute Received: from 003.mia.mailroute.net ([127.0.0.1]) by localhost (003.mia [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id fx8_Kpnf0S6p; Mon, 24 Mar 2025 10:58:45 +0000 (UTC) Received: from [172.22.32.156] (unknown [99.209.85.25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 003.mia.mailroute.net (Postfix) with ESMTPSA id 4ZLqm46VPpzm8kw7; Mon, 24 Mar 2025 10:58:27 +0000 (UTC) Message-ID: Date: Mon, 24 Mar 2025 06:58:26 -0400 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 2/4] blkdev: lift BLK_MAX_BLOCK_SIZE to page cache limit To: Matthew Wilcox Cc: Luis Chamberlain , leon@kernel.org, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@kernel.dk, joro@8bytes.org, brauner@kernel.org, hare@suse.de, david@fromorbit.com, djwong@kernel.org, john.g.garry@oracle.com, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, kernel@pankajraghav.com References: <20250320111328.2841690-1-mcgrof@kernel.org> <20250320111328.2841690-3-mcgrof@kernel.org> <5459e3e0-656c-4d94-82c7-3880608f9ac8@acm.org> Content-Language: en-US From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/20/25 12:27 PM, Matthew Wilcox wrote: > On Thu, Mar 20, 2025 at 09:15:23AM -0700, Bart Van Assche wrote: >> The patch description mentions what has been changed but does not >> mention why. Shouldn't the description of this patch explain why this >> change has been made? Shouldn't the description of this patch explain >> for which applications this change is useful? > > The manufacturer chooses the block size. If they've made a bad decision, > their device will presumably not sell well. We don't need to justify > their decision in the commit message. From a 2023 presentation by Luis (https://lpc.events/event/17/contributions/1508/attachments/1298/2608/LBS_LPC2023.pdf): - SSD manufacturers want to increase the indirection unit (IU) size. - Increasing the IU size reduces SSD DRAM costs. - LBS is not suitable for all workloads because smaller IOs with LBS can cause write amplification (WAF) due to read modify writes. - Some database software benefits of a 16 KiB logical block size. If the goal is to reduce DRAM costs then I recommend SSD manufacturers to implement zoned storage (ZNS) instead of only increasing the logical block size. A big advantage of zoned storage is that the DRAM cost is reduced significantly even if the block size is not increased. Are there any applications that benefit from a block size larger than 64 KiB? If not, why to increase BLK_MAX_BLOCK_SIZE further? Do you agree that this question should be answered in the patch description? Thanks, Bart.