linux-kernel - Re: [PATCH] nvme-pci: 512 byte dma pool segment quirk

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Message-ID: <20241108070806.GA9216@lst.de>
Date: Fri, 8 Nov 2024 08:08:06 +0100
From: Christoph Hellwig <hch@....de>
To: Keith Busch <kbusch@...nel.org>
Cc: Bob Beckett <bob.beckett@...labora.com>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	kernel@...labora.com, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: 512 byte dma pool segment quirk

On Thu, Nov 07, 2024 at 10:19:30AM -0700, Keith Busch wrote:
> We have a constant expression currently, and this is changing it a full
> division in the IO path. :(

Yeah.  Given that the device is broken I'd just have it pay the price
and never use the small prp pool instead, which just adds a single
extra branch to the fast path.