linux-kernel - Re: [RFC PATCH 2/7] block: don't merge different kinds of P2P transfers in a single bio

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Message-ID: <9db04bd9-81e1-4e60-a590-0882cd86052f@deltatee.com>
Date: Mon, 28 Oct 2024 12:27:51 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: Leon Romanovsky <leon@...nel.org>, Jens Axboe <axboe@...nel.dk>,
 Jason Gunthorpe <jgg@...pe.ca>, Robin Murphy <robin.murphy@....com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>
Cc: Keith Busch <kbusch@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Yishai Hadas <yishaih@...dia.com>,
 Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
 Kevin Tian <kevin.tian@...el.com>,
 Alex Williamson <alex.williamson@...hat.com>,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Jérôme Glisse <jglisse@...hat.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Jonathan Corbet <corbet@....net>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-block@...r.kernel.org, linux-rdma@...r.kernel.org,
 iommu@...ts.linux.dev, linux-nvme@...ts.infradead.org,
 linux-pci@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/7] block: don't merge different kinds of P2P
 transfers in a single bio



On 2024-10-27 08:21, Leon Romanovsky wrote:
> From: Christoph Hellwig <hch@....de>
> 
> To get out of the dma mapping helpers having to check every segment for
> it's P2P status, ensure that bios either contain P2P transfers or non-P2P
> transfers, and that a P2P bio only contains ranges from a single device.
> 
> This means we do the page zone access in the bio add path where it should
> be still page hot, and will only have do the fairly expensive P2P topology
> lookup once per bio down in the dma mapping path, and only for already
> marked bios.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>

Looks good to me.

Reviewed-by: Logan Gunthorpe <logang@...tatee.com>