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 55007C25B7E for ; Fri, 31 May 2024 05:55:09 +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=Fz4Bv4M5AAT14OTvNn8yFGaSkoztSkte1YX9/kljUAw=; b=YnazTGI2NmQPg2iOoGF6dIF3/Z oAaUNcypJ9qPk48WYPPPQAeKsEBRj+iXgD0FjfcZg5V9GfTHjDfUmgeV8rGTyac+mGgLdjZMFiaQK V065gAsDMF0H3MCWP85QIH9hBdNP+T9ZU1SGt+yIPgFtq5ORiLGcQpiDhchD+rzjmAFdUYl3FTPfY P2mIpf1dRh6m3pZNDCJxFrEusvTcK5SPPuuuBFzx6Mg0cCu9ZX8eIouz2KFOIUn8Im5yZiNIUPZdN YnLHAnTsq6La90vrtA91MR1D6Y1Wx/z3YsqFy4aanyB5SwIgo7APrHHLTcd71SQzbuZzpwIEYSWJb 5/9Gr/ag==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCvEJ-00000009Jaj-47WH; Fri, 31 May 2024 05:55:08 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCvEG-00000009Ja8-1bkw for linux-um@lists.infradead.org; Fri, 31 May 2024 05:55:05 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id D3CD568BFE; Fri, 31 May 2024 07:54:56 +0200 (CEST) Date: Fri, 31 May 2024 07:54:56 +0200 From: Christoph Hellwig To: Ilya Dryomov Cc: Christoph Hellwig , Jens Axboe , "Martin K. Petersen" , Richard Weinberger , Anton Ivanov , Johannes Berg , Josef Bacik , Dongsheng Yang , Roger Pau Monn?? , linux-um@lists.infradead.org, linux-block@vger.kernel.org, nbd@other.debian.org, ceph-devel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH 02/12] block: take io_opt and io_min into account for max_sectors Message-ID: <20240531055456.GC17396@lst.de> References: <20240529050507.1392041-1-hch@lst.de> <20240529050507.1392041-3-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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-20240530_225504_590510_E77DA6FF X-CRM114-Status: GOOD ( 19.02 ) X-BeenThere: linux-um@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-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org On Thu, May 30, 2024 at 09:48:06PM +0200, Ilya Dryomov wrote: > For rbd, this change effectively lowers max_sectors from 4M to 64K or > less and that is definitely not desirable. From previous interactions > with users we want max_sectors to match max_hw_sectors -- this has come > up a quite a few times over the years. Some people just aren't aware > of the soft cap and the fact that it's adjustable and get frustrated > over the time poured into debugging their iostat numbers for workloads > that can send object (set) size I/Os. > > Looking at the git history, we lowered io_opt from objset_bytes to > opts->alloc_size in commit [1], but I guess io_opt was lowered just > along for the ride. What that commit was concerned with is really > discard_granularity and to a smaller extent io_min. > > How much difference does io_opt make in the real world? If what rbd > does stands in the way of a tree-wide cleanup, I would much rather bump > io_opt back to objset_bytes (i.e. what max_user_sectors is currently > set to). The only existing in-kernel usage is to set the readahead size. Based on your comments I seems like we should revert io_opt to objset to ->alloc_size in a prep patch?