From: Christoph Hellwig <hch@lst.de>
To: Leon Romanovsky <leon@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>,
Keith Busch <kbusch@meta.com>,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH] nvme-pci: always use blk_map_iter for metadata
Date: Mon, 27 Oct 2025 08:13:53 +0100 [thread overview]
Message-ID: <20251027071353.GA13854@lst.de> (raw)
In-Reply-To: <20251026072551.GB12554@unreal>
On Sun, Oct 26, 2025 at 09:25:51AM +0200, Leon Romanovsky wrote:
> > Maybe the data path should only use blk_dma_iter too. Is dma_map_bvec
> > that much faster for the single vector case? I'm going to test both on
> > real hardware and see if there's a difference in CPU utilization or
> > latency.
>
> We tried that path (remove special case for single segment), but for
> very performance oriented case: direct mode without IOMMU, no p2p and
> extremely powerful RAID (~94M IOPS), Jens and Kanchan saw performance
> drop. On consumer grade HW (~2M IOPS), the performance change was not
> noticed.
Yes. Sorry, I wanted to reply something like this to Keith earlier but
managed to drop the ball.
next prev parent reply other threads:[~2025-10-27 7:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-20 18:24 [PATCH] nvme-pci: always use blk_map_iter for metadata Keith Busch
2025-10-20 23:38 ` Chaitanya Kulkarni
2025-10-21 7:19 ` Christoph Hellwig
2025-10-21 14:42 ` Keith Busch
2025-10-26 7:25 ` Leon Romanovsky
2025-10-27 7:13 ` Christoph Hellwig [this message]
2025-10-27 16:09 ` Keith Busch
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