From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
linux-mm@kvack.org, John Hubbard <jhubbard@nvidia.com>,
David Howells <dhowells@redhat.com>,
David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH 1/5] mm: Do not reclaim private data from pinned page
Date: Mon, 13 Feb 2023 01:55:04 -0800 [thread overview]
Message-ID: <Y+oI+AYsADUZsB7m@infradead.org> (raw)
In-Reply-To: <20230210112954.3yzlyi4hjgci36yn@quack3>
On Fri, Feb 10, 2023 at 12:29:54PM +0100, Jan Kara wrote:
> functionally that would make sense but as I've mentioned in my reply to you
> [1], the problem here is the performance. I've now dug out the discussion
> from 2018 where John actually tried to take pinned pages out of the LRU [2]
> and the result was 20% IOPS degradation on his NVME drive because of the
> cost of taking the LRU lock. I'm not even speaking how costly that would
> get on any heavily parallel direct IO workload on some high-iops device...
I think we need to distinguish between short- and long terms pins.
For short term pins like direct I/O it doesn't make sense to take them
off the lru, or to do any other special action. Writeback will simplify
have to wait for the short term pin.
Long-term pins absolutely would make sense to be taken off the LRU list.
next prev parent reply other threads:[~2023-02-13 9:55 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 12:31 [PATCH RFC 0/5] Writeback handling of pinned pages Jan Kara
2023-02-09 12:31 ` [PATCH 1/5] mm: Do not reclaim private data from pinned page Jan Kara
2023-02-09 16:17 ` Matthew Wilcox
2023-02-10 11:29 ` Jan Kara
2023-02-13 9:55 ` Christoph Hellwig [this message]
2023-02-14 13:06 ` Jan Kara
2023-02-14 21:40 ` John Hubbard
2023-02-16 11:56 ` Jan Kara
2023-02-13 9:01 ` David Hildenbrand
2023-02-14 13:00 ` Jan Kara
2023-02-09 12:31 ` [PATCH 2/5] ext4: Drop workaround for mm reclaiming fs private page data Jan Kara
2023-02-09 12:31 ` [PATCH 3/5] mm: Do not try to write pinned folio during memory cleaning writeback Jan Kara
2023-02-10 1:54 ` John Hubbard
2023-02-10 2:10 ` John Hubbard
2023-02-10 10:42 ` Jan Kara
2023-02-10 10:54 ` Jan Kara
2023-02-09 12:31 ` [PATCH 4/5] block: Add support for bouncing pinned pages Jan Kara
2023-02-13 9:59 ` Christoph Hellwig
2023-02-14 13:56 ` Jan Kara
2023-02-15 4:59 ` Dave Chinner
2023-02-15 6:24 ` Christoph Hellwig
2023-02-16 12:33 ` Jan Kara
2023-02-20 6:22 ` Christoph Hellwig
2023-02-27 11:39 ` Jan Kara
2023-02-27 13:36 ` Christoph Hellwig
2023-02-09 12:31 ` [PATCH 5/5] iomap: Bounce pinned pages during writeback Jan Kara
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