From: David Hildenbrand <david@redhat.com>
To: Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>
Cc: Sooyong Suk <s.suk@samsung.com>,
viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, linux-mm@kvack.org,
jaewon31.kim@gmail.com, spssyr@gmail.com
Subject: Re: [RFC PATCH] block, fs: use FOLL_LONGTERM as gup_flags for direct IO
Date: Thu, 13 Mar 2025 23:49:00 +0100 [thread overview]
Message-ID: <cd013218-7735-4bc1-b6b6-80d1129e2b76@redhat.com> (raw)
In-Reply-To: <Z9GmYe-bdOZ8LQV5@infradead.org>
On 12.03.25 16:21, Christoph Hellwig wrote:
> On Fri, Mar 07, 2025 at 08:23:08PM +0000, Matthew Wilcox wrote:
>> Howver, the problem is real.
>
> What is the problem?
I think the problem is the CMA allocation failure, not the latency.
"if a large amount of direct IO is requested constantly, this can make
pages in CMA pageblocks pinned and unable to migrate outside of the
pageblock"
We'd need a more reliable way to make CMA allocation -> page migration
make progress. For example, after we isolated the pageblocks and
migration starts doing its thing, we could disallow any further GUP
pins. (e.g., make GUP spin or wait for migration to end)
We could detect in GUP code that a folio is soon expected to be migrated
by checking the pageblock (isolated) and/or whether the folio is locked.
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2025-03-13 22:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20250306074101epcas1p4b24ac546f93df2c7fe3176607b20e47f@epcas1p4.samsung.com>
2025-03-06 7:40 ` Sooyong Suk
2025-03-06 15:26 ` Christoph Hellwig
2025-03-06 23:28 ` Jaewon Kim
2025-03-07 2:07 ` Sooyong Suk
2025-03-07 2:28 ` Suren Baghdasaryan
2025-03-07 6:38 ` Sooyong Suk
2025-03-12 15:17 ` Christoph Hellwig
2025-03-12 15:20 ` Suren Baghdasaryan
2025-03-12 15:25 ` Christoph Hellwig
2025-03-12 15:38 ` Suren Baghdasaryan
2025-03-12 15:52 ` Christoph Hellwig
2025-03-12 16:03 ` Bart Van Assche
2025-03-12 16:06 ` Suren Baghdasaryan
2025-03-12 16:21 ` Christoph Hellwig
2025-03-07 20:23 ` Matthew Wilcox
2025-03-07 21:37 ` Suren Baghdasaryan
2025-03-12 15:21 ` Christoph Hellwig
2025-03-13 22:49 ` David Hildenbrand [this message]
2025-03-15 1:04 ` John Hubbard
2025-03-15 23:00 ` David Hildenbrand
2025-03-15 23:09 ` Zi Yan
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