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 094ABCF3187 for ; Wed, 19 Nov 2025 09:55:28 +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=N3St2NZBhXRGn9n9RacTN/Cn2H10NSydjlI4KDiDHIA=; b=pwS92fNGt+BUptBDfPJJ1U/YyG 1KdSqddQGHPNY66k+PRsvQeoUVSNt44Y6cxvU5edoW+jhqXmSlbx9Tu15rS+/kaqDEtb7g1irSTlX yhgwmD8iCFmojnUWU1a3MO+eDxU6WJQPZ3LnfOBDPq0ZjwS10p//4L53n9/jKcz+v6Q3oaqY1ShID gfpBG9CZUMgA1pT4lf9cZjiNKOzVIADusYrkMsXJtbDHTWgr6tBuJ884tnJaYzjowxNgjes4Xh/2z vyt2Gkz0oZ790hTTHuPkqEXhvC+9mUulyIq56Aux7Mb2XCp8VCbtTFY1AM4LY9qYgJEOUY61d4apC +uceiotw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vLeuK-00000002uKd-2x4T; Wed, 19 Nov 2025 09:55:24 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vLeuJ-00000002uKH-304r for linux-nvme@lists.infradead.org; Wed, 19 Nov 2025 09:55:23 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id D584B60123; Wed, 19 Nov 2025 09:55:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E9E4C2BCB8; Wed, 19 Nov 2025 09:55:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763546122; bh=mrVGDGmdBwi9bp1Ejm5GWoCivDI1+7VKZSTga3B+PrE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=alOJWxNcB+IkVtIDy2pVEUyd3HFS7OmaPY1pgPwYQvu0rHyh4x9n+9brKyMNnQv/v Qq/pe+VC1Nn/fpd6n+LbqNwfMRfVwcZyFTRG9+u0KDEVY3w/5Nv8tE9d3P22QKl/hD ztmwVEfvJ0g6Z2VTO63PE09RkTkimEuutWrCDWxFDze1ym4BLGuNL9hxxXIht6x24v CYHHKFl99vhFfpGb9egB0srcRsR/HhSNEixF0MUs7KHQ+lo8AjkCSqBApb9DMnEPwH M8L5MtlUI6wysxhIXBD2Z4QIm/rkq6+k+Vo8w9R9p7oCQKVHOUgpNF1oEmeNXonWg1 E0y9b6mcngrEQ== Date: Wed, 19 Nov 2025 11:55:16 +0200 From: Leon Romanovsky To: Christoph Hellwig Cc: Jens Axboe , Keith Busch , Sagi Grimberg , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Chaitanya Kulkarni Subject: Re: [PATCH v2 1/2] nvme-pci: Use size_t for length fields to handle larger sizes Message-ID: <20251119095516.GA13783@unreal> References: <20251117-nvme-phys-types-v2-0-c75a60a2c468@nvidia.com> <20251117-nvme-phys-types-v2-1-c75a60a2c468@nvidia.com> <20251118050311.GA21569@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251118050311.GA21569@lst.de> 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 Tue, Nov 18, 2025 at 06:03:11AM +0100, Christoph Hellwig wrote: > On Mon, Nov 17, 2025 at 09:22:43PM +0200, Leon Romanovsky wrote: > > From: Leon Romanovsky > > > > This patch changes the length variables from unsigned int to size_t. > > Using size_t ensures that we can handle larger sizes, as size_t is > > always equal to or larger than the previously used u32 type. > > > > Originally, u32 was used because blk-mq-dma code evolved from > > scatter-gather implementation, which uses unsigned int to describe length. > > This change will also allow us to reuse the existing struct phys_vec in places > > that don't need scatter-gather. > > > > Signed-off-by: Leon Romanovsky > > Reviewed-by: Chaitanya Kulkarni > > --- > > block/blk-mq-dma.c | 8 ++++++-- > > drivers/nvme/host/pci.c | 4 ++-- > > 2 files changed, 8 insertions(+), 4 deletions(-) > > > > diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c > > index e9108ccaf4b0..e7d9b54c3eed 100644 > > --- a/block/blk-mq-dma.c > > +++ b/block/blk-mq-dma.c > > @@ -8,7 +8,7 @@ > > > > struct phys_vec { > > phys_addr_t paddr; > > - u32 len; > > + size_t len; > > }; > > So we're now going to increase memory usage by 50% again after just > reducing it by removing the scatterlist? It is slightly less. Before this change: 96 bits After this change (on 64bits system): 128 bits. It is 33% increase per-structure. So what is the resolution? Should I drop this patch or not? Thanks