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Date: Thu, 20 Mar 2025 15:18:46 +0100
From: Christoph Hellwig <hch@lst.de>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
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Subject: Re: [LSF/MM/BPF TOPIC] breaking the 512 KiB IO boundary on x86_64
Message-ID: <20250320141846.GA11512@lst.de>
References: <Z9v-1xjl7dD7Tr-H@bombadil.infradead.org>
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On Thu, Mar 20, 2025 at 04:41:11AM -0700, Luis Chamberlain wrote:
> We've been constrained to a max single 512 KiB IO for a while now on x86_64.

No, we absolutely haven't.  I'm regularly seeing multi-MB I/O on both
SCSI and NVMe setup.

> This is due to the number of DMA segments and the segment size.

In nvme the max_segment_size is UINT_MAX, and for most SCSI HBAs it is
fairly large as well.