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 DC9CDC3ABCC for ; Wed, 14 May 2025 14:39:12 +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=HSeLQgCeSnJO9MrfHW3OsAe0wmIEhjCN/0Vyr6nJ/sA=; b=2TypTuE+iRN3R0tbabNbHZLarm iKhpW8fJr6V702jTTV4NxY5rm/a33mBdF4EgAz7HNDGYY/e7tIcsHtphpCX46tR6JXmm75tifWi5l BBO1hY5VgUmriaQe4Bq7RZ8re2GDJT1sfqv1z9k2CHYUV0oXCfinNEUNXDmCBmIyF6u5cE4Yw1u06 mFaQHA4FcknFLaVNQN5yWVobQicnEVck/9Io8XjeYE0mGFiFM6GbUU5ty+iiVBYOCnJbBAEwMZ1EM NwdSYTQcjPVn0UpnG00Go1UuAu9IUh6ass+nesM1wHCDfAnwRf2NlTl/Wp4uJyfSfmEz+R9Z0icSi O/daSybg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uFDGJ-0000000FR9a-1wQk; Wed, 14 May 2025 14:39:11 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uFCeV-0000000FLoI-3735 for linux-nvme@lists.infradead.org; Wed, 14 May 2025 14:00:09 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id E3FEC68AFE; Wed, 14 May 2025 16:00:00 +0200 (CEST) Date: Wed, 14 May 2025 16:00:00 +0200 From: Christoph Hellwig To: Keith Busch Cc: Christoph Hellwig , Sagi Grimberg , Caleb Sander Mateos , Leon Romanovsky , linux-nvme@lists.infradead.org Subject: Re: [PATCH 5/7] nvme-pci: use a better encoding for small prp pool allocations Message-ID: <20250514140000.GB25649@lst.de> References: <20250513070025.830930-1-hch@lst.de> <20250513070025.830930-6-hch@lst.de> <20250514051221.GD24101@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-20250514_070007_919320_8F8D4DF7 X-CRM114-Status: GOOD ( 15.21 ) 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 Wed, May 14, 2025 at 07:06:17AM -0600, Keith Busch wrote: > But if you are trying to merge dozens of requests with metadata into > one, then yeah, the small pool isn't large enough to accomodate. If you > want to support that use case, then we can certainly change the driver > to use the large pool when more than 15 integrity segments are required. Merge is one use case. The other is to use non-contigous buffers for file system PI support, as a single BIO with large folios can get quite huge, and being able to either use vmalloc or multiple pages would be very helpful there.