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 5030AC02193 for ; Mon, 3 Feb 2025 08:06:49 +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=r1r6plQaRoAy1Nxbdg0BWrNM7QAkG9cm/NIMqGIem9Y=; b=lVtZ+ZHS9ehMmdFaOWf3k3vfRp QWNPPjpjV063zbfVYwBTgy1ZCKtyRhikv58jAru95Eheb49dsVmBrvCqqnJcD2CphK5itcRlo0Ml1 qJAbRWSYCXLxuhyHRV+sObKUWsrM7PdqRFlRW5owwd/4u8Md+RnOCeMpThgge5G1b1Qv2DVnNzPF3 jLPLOsAT7OJDkkD2BPE7tAmw403DEUZ5ssQioXulGS/kW10i8+R74NpYMFgfNA990XVOcFrZR3Oag h5TVXSpudi1ppr9aCmhi7b/sTNTMAaWg4ZJRkzJsdFKKvcJ3cNZjaVklTkd2EG7dI0YsjgBdZ6ph0 3RGflQ1w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1terTj-0000000Else-3UiY; Mon, 03 Feb 2025 08:06:47 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1terTh-0000000ElsK-1hgZ; Mon, 03 Feb 2025 08:06:45 +0000 Date: Mon, 3 Feb 2025 00:06:45 -0800 From: "hch@infradead.org" To: Johannes Thumshirn Cc: "hch@infradead.org" , Kanchan Joshi , Theodore Ts'o , "lsf-pc@lists.linux-foundation.org" , "linux-btrfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "josef@toxicpanda.com" Subject: Re: [LSF/MM/BPF TOPIC] File system checksum offload Message-ID: References: <20250130091545.66573-1-joshi.k@samsung.com> <20250130142857.GB401886@mit.edu> <97f402bc-4029-48d4-bd03-80af5b799d04@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 On Mon, Feb 03, 2025 at 08:04:42AM +0000, Johannes Thumshirn wrote: > Well for the WAF part, it'll save us 32 Bytes per FS sector (typically > 4k) in the btrfs case, that's ~0.8% of the space. It saves you from the cascading btree updates. With nocow this could actually allow btrfs to write with WAF=1 for pure overwrites. But even with data cow it will reduce a lot of churn, especially for O_SYNC writes.