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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FC3BC4332F for ; Mon, 10 Jan 2022 23:30:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244408AbiAJXaa (ORCPT ); Mon, 10 Jan 2022 18:30:30 -0500 Received: from mx.ewheeler.net ([173.205.220.69]:47288 "EHLO mx.ewheeler.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241114AbiAJXa2 (ORCPT ); Mon, 10 Jan 2022 18:30:28 -0500 Received: from localhost (localhost [127.0.0.1]) by mx.ewheeler.net (Postfix) with ESMTP id 26AC54A; Mon, 10 Jan 2022 15:30:27 -0800 (PST) X-Virus-Scanned: amavisd-new at ewheeler.net Received: from mx.ewheeler.net ([127.0.0.1]) by localhost (mx.ewheeler.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 7WW_Nc2i1HIQ; Mon, 10 Jan 2022 15:30:26 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx.ewheeler.net (Postfix) with ESMTPSA id 3F41E39; Mon, 10 Jan 2022 15:30:26 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 mx.ewheeler.net 3F41E39 Date: Mon, 10 Jan 2022 15:30:24 -0800 (PST) From: Eric Wheeler To: "Martin K. Petersen" cc: Kent Overstreet , Coly Li , linux-block@vger.kernel.org, Jonathan Corbet , "open list:DOCUMENTATION" , open list , "open list:BCACHE (BLOCK LAYER CACHE)" Subject: Re: [PATCH] bcache: make stripe_size configurable and persistent for hardware raid5/6 In-Reply-To: Message-ID: <611f98fc-222-8dd2-6b81-d570fb91fc@ewheeler.net> References: <1561245371-10235-1-git-send-email-bcache@lists.ewheeler.net> <200638b0-7cba-38b4-20c4-b325f3cfe862@suse.de> <8a9131dc-9bf7-a24a-f7b8-35e0c019e905@suse.de> <98aa1886-859-abb9-164f-c9eb9be38a91@ewheeler.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Jan 2022, Martin K. Petersen wrote: > > Ok so `git blame` shows that Kent added this to md/raid5.c in > > c78afc6261b (Kent Overstreet 2013-07-11 22:39:53 -0700 7526) > > Yep. > > > Do you think we should leave the md-specific > > raid_partial_stripes_expensive setting and require users of RAID > > controllers to set the bit themselves in bcache---or---remove all > > raid_partial_stripes_expensive code and always treat writes as > > "expensive" when `opt_io` is defined? > > I'd prefer the latter since that was the very intent of exporting the > device topology in an abstract and protocol-independent fashion. > However, I don't know enough about bcache internals to know whether it > is always the right choice, what the trade-offs are, etc. I've not looked in detail, but I don't think its too difficult. Do you know if io_opt can be configured on scsi devices that do not have io_opt provided by the controller? If so, or if it would be easy to add, then configuring io_opt at the scsi layer is probably a better option so subsystems besides bcache would benefit. What do you think? -- Eric Wheeler > > -- > Martin K. Petersen Oracle Linux Engineering >