From: Luis Chamberlain <mcgrof@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-block@vger.kernel.org, lsf-pc@lists.linux-foundation.org,
david@fromorbit.com, leon@kernel.org, kbusch@kernel.org,
sagi@grimberg.me, axboe@kernel.dk, joro@8bytes.org,
brauner@kernel.org, hare@suse.de, willy@infradead.org,
djwong@kernel.org, john.g.garry@oracle.com,
ritesh.list@gmail.com, p.raghav@samsung.com,
gost.dev@samsung.com, da.gomez@samsung.com
Subject: Re: [LSF/MM/BPF TOPIC] breaking the 512 KiB IO boundary on x86_64
Date: Thu, 20 Mar 2025 14:40:52 -0700 [thread overview]
Message-ID: <Z9yLZAjrHFsCD1Ww@bombadil.infradead.org> (raw)
In-Reply-To: <20250320141846.GA11512@lst.de>
On Thu, Mar 20, 2025 at 03:18:46PM +0100, Christoph Hellwig wrote:
> 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.
Sorry you're right, I should have been clearer. This is only an issue without
large folios for buffered IO, or without scatter list chaining support.
Or put another way, block driver which don't support scatter list
chaining will end up with a different max IO possible for direct IO and
io-uring cmd.
> > 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.
For Direct IO or io-uring cmd when large folios may not be used the
segments will be constrained to the page size.
Luis
next prev parent reply other threads:[~2025-03-20 21:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-20 11:41 Luis Chamberlain
2025-03-20 12:11 ` Matthew Wilcox
2025-03-20 13:29 ` Daniel Gomez
2025-03-20 14:31 ` Matthew Wilcox
2025-03-20 13:47 ` Daniel Gomez
2025-03-20 14:54 ` Christoph Hellwig
2025-03-21 9:14 ` Daniel Gomez
2025-03-20 14:18 ` Christoph Hellwig
2025-03-20 15:37 ` Bart Van Assche
2025-03-20 15:58 ` Keith Busch
2025-03-20 16:13 ` Kanchan Joshi
2025-03-20 16:38 ` Christoph Hellwig
2025-03-20 21:50 ` Luis Chamberlain
2025-03-20 21:46 ` Luis Chamberlain
2025-03-20 21:40 ` Luis Chamberlain [this message]
2025-03-20 18:46 ` Ritesh Harjani
2025-03-20 21:30 ` Darrick J. Wong
2025-03-21 2:13 ` Ritesh Harjani
2025-03-21 3:05 ` Darrick J. Wong
2025-03-21 4:56 ` Theodore Ts'o
2025-03-21 5:00 ` Christoph Hellwig
2025-03-21 18:39 ` Ritesh Harjani
2025-03-21 16:38 ` Keith Busch
2025-03-21 17:21 ` Ritesh Harjani
2025-03-21 18:55 ` Keith Busch
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