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 5CE42D5D66B for ; Thu, 7 Nov 2024 17:19:42 +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=46zMNri+AGeiznjDoZX8tvclnTDWBiZ0BDALNHQI+e4=; b=wCtbiZq24MUdAdqMJnthXzm8O6 MU56tVeai3cjAPUyZRBz6n+Zuw+G0qHSfLlDLoOxfmWFvwMWacKrzr0PQbClBnmhif3h08CA+8Pbs faHiMPtZp4Y1NDkTnYQNv+DHMesRM3hrMhdWny25sqDQ/hNi1pVk6ELfA8XdhIizbIrIewDAPR6in o+FThz8lE1dldhjIbTzUwBy1YbJUydBjr61TYTzdYUxEpD7s9Hka7brTgEFgkG55KgowMzE9agiMD B3h/SEPhgSSqgk4CLv2bkfzH7WMkaCJ4vFwDtpbE+zmnz/Me/FTdS6mhy55pyQ8Ea/BfZSJvRIbHa DNal7A+w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t96AU-00000007n2A-3HHA; Thu, 07 Nov 2024 17:19:38 +0000 Received: from nyc.source.kernel.org ([2604:1380:45d1:ec00::3]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t96AR-00000007n1j-1CGI for linux-nvme@lists.infradead.org; Thu, 07 Nov 2024 17:19:36 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 2F5D5A448A8; Thu, 7 Nov 2024 17:17:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21AE5C4CECC; Thu, 7 Nov 2024 17:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730999973; bh=oqZnj3nucJM60cIfyc8kf3ErFRrH9f1YRFHIGBlSDro=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZO4aapRuNnHDr8oE2VhQbb6eD/aCiUzQ0QCwJtmx5kq9fLA/RKhVj2VZH1BQ+A2Pc C7cJhTNV9krDdMGUU5BU10lPglIhzNPQ3Z4YqMt+ukpnYUOXU5LWjxdTUtI4opsGR2 cSZg0l1/JDjMcj2Gm4cnAfptdozTrTX8sgEGa4FlnMd4UYjpqtfpTJFb2LVwkFx4xU Be8FrrN/yIeL2iCExkraxkZZTMeVyl/6Cz4Yjm1iy4OC0cMII4QN5i2691DAWECwjh q6moo3TENq9iASogpJF+4J9XcMY4JxPcO0JC593P4qOonQYRsccYI75Of1EWGDYqh+ RLVMJz3G26sog== Date: Thu, 7 Nov 2024 10:19:30 -0700 From: Keith Busch To: Bob Beckett Cc: Jens Axboe , Christoph Hellwig , Sagi Grimberg , kernel@collabora.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] nvme-pci: 512 byte dma pool segment quirk Message-ID: References: <20241107165131.3462171-1-bob.beckett@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241107165131.3462171-1-bob.beckett@collabora.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241107_091935_408008_A29765B6 X-CRM114-Status: GOOD ( 14.94 ) 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 Thu, Nov 07, 2024 at 04:50:46PM +0000, Bob Beckett wrote: > @@ -611,7 +612,7 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev, > } > > nprps = DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE); > - if (nprps <= (256 / 8)) { > + if (nprps <= (dev->small_dmapool_seg_size / 8)) { > pool = dev->prp_small_pool; > iod->nr_allocations = 0; > } else { We have a constant expression currently, and this is changing it a full division in the IO path. :( Could we leave the pool selection check size as-is and just say the cost of the quirk is additional memory overhead? > @@ -2700,8 +2701,9 @@ static int nvme_setup_prp_pools(struct nvme_dev *dev) > return -ENOMEM; > > /* Optimisation for I/Os between 4k and 128k */ > - dev->prp_small_pool = dma_pool_create("prp list 256", dev->dev, > - 256, 256, 0); > + dev->prp_small_pool = dma_pool_create("prp list small", dev->dev, > + dev->small_dmapool_seg_size, > + dev->small_dmapool_seg_size, 0); I think it should work if we only change the alignment property of the pool. Something like this: if (dev->ctrl.quirks & NVME_QUIRK_SMALL_DMAPOOL_512) dev->prp_small_pool = dma_pool_create("prp list 256", dev->dev, 256, 512, 0); else dev->prp_small_pool = dma_pool_create("prp list 256", dev->dev, 256, 256, 0);