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 EE841FA3758 for ; Wed, 18 Sep 2024 06:43:17 +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=Mgkp1hVF8HPPXGHzeffL9DY1/PZ+CgypD5IansUpcKo=; b=dA0xOCk0EE2+sUpt6i9tSf+Rbc tHr1KGE9PIlpatx1H2rIroL0dNyJ/cR4yHpKS4zmzouZV/ef0/7rloc6luki3IwJMzslGie3Trzy6 0q4q2/9vufyTAovX6/rXzyjbrm/xdCssfIZ5PAIj2gAETiMHyNZ0dv9aC1CDsrL5Igt4wNz1c/6Va t+kMkwTwEwCAU+IGR+CNydatioTI0rpOq3lfJeI4iZM+/CJyWEfzsCLpkXUvDpJYqGXnNY6Ty8vj2 qsFF6g89HbGFubb8eCuTQbv4rboxgaL3sEiUdyutl/KM6sjssS6fp6zeHaSyZsh0oh4KZMK6X2Tp6 N+E2K9nw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1sqoPB-00000007ZeA-3bv0; Wed, 18 Sep 2024 06:43:13 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1sqoP9-00000007Zcw-1JoX for linux-nvme@lists.infradead.org; Wed, 18 Sep 2024 06:43:12 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 0186F227A88; Wed, 18 Sep 2024 08:42:59 +0200 (CEST) Date: Wed, 18 Sep 2024 08:42:58 +0200 From: Christoph Hellwig To: Kanchan Joshi Cc: Christoph Hellwig , axboe@kernel.dk, kbusch@kernel.org, sagi@grimberg.me, martin.petersen@oracle.com, James.Bottomley@HansenPartnership.com, brauner@kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, jaegeuk@kernel.org, jlayton@kernel.org, chuck.lever@oracle.com, bvanassche@acm.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, gost.dev@samsung.com, vishak.g@samsung.com, javier.gonz@samsung.com, Nitesh Shetty Subject: Re: [PATCH v5 4/5] sd: limit to use write life hints Message-ID: <20240918064258.GA32627@lst.de> References: <20240910150200.6589-1-joshi.k@samsung.com> <20240910150200.6589-5-joshi.k@samsung.com> <20240912130235.GB28535@lst.de> <20240913080659.GA30525@lst.de> <4a39215a-1b0e-3832-93bd-61e422705f8b@samsung.com> <20240917062007.GA4170@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-20240917_234311_523654_7C5B97DC X-CRM114-Status: GOOD ( 19.03 ) 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 > > If the device (or file system, which really needs to be in control > > for actual files vs just block devices) does not support all 256 > > we need to reduce them to less than that. The kernel can help with > > that a bit if the streams have meanings (collapsing temperature levels > > that are close), but not at all if they don't have meanings. > > Current patch (nvme) does what you mentioned above. > Pasting the fragment that maps potentially large placement-hints to the > last valid placement-id. > > +static inline void nvme_assign_placement_id(struct nvme_ns *ns, > + struct request *req, > + struct nvme_command *cmd) > +{ > + u8 h = umin(ns->head->nr_plids - 1, > + WRITE_PLACEMENT_HINT(req->write_hint)); > + > + cmd->rw.control |= cpu_to_le16(NVME_RW_DTYPE_DPLCMT); > + cmd->rw.dsmgmt |= cpu_to_le32(ns->head->plids[h] << 16); > +} > > But this was just an implementation choice (and not a failure avoidance > fallback). And it completely fucks thing up as I said. If I have an application that wants to separate streams I need to know how many stream I have available, and not fold all higher numbers into the last one available.