From: Matthew Wilcox <willy@infradead.org>
To: Xu Yang <xu.yang_2@nxp.com>
Cc: brauner@kernel.org, djwong@kernel.org, akpm@linux-foundation.org,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, jun.li@nxp.com
Subject: Re: [PATCH v5 2/2] iomap: fault in smaller chunks for non-large folio mappings
Date: Fri, 24 May 2024 13:18:38 +0100 [thread overview]
Message-ID: <ZlCFnlXPPUo_0mYX@casper.infradead.org> (raw)
In-Reply-To: <20240521114939.2541461-2-xu.yang_2@nxp.com>
On Tue, May 21, 2024 at 07:49:39PM +0800, Xu Yang wrote:
> Since commit (5d8edfb900d5 "iomap: Copy larger chunks from userspace"),
> iomap will try to copy in larger chunks than PAGE_SIZE. However, if the
> mapping doesn't support large folio, only one page of maximum 4KB will
> be created and 4KB data will be writen to pagecache each time. Then,
> next 4KB will be handled in next iteration. This will cause potential
> write performance problem.
>
> If chunk is 2MB, total 512 pages need to be handled finally. During this
> period, fault_in_iov_iter_readable() is called to check iov_iter readable
> validity. Since only 4KB will be handled each time, below address space
> will be checked over and over again:
>
> start end
> -
> buf, buf+2MB
> buf+4KB, buf+2MB
> buf+8KB, buf+2MB
> ...
> buf+2044KB buf+2MB
>
> Obviously the checking size is wrong since only 4KB will be handled each
> time. So this will get a correct chunk to let iomap work well in non-large
> folio case.
>
> With this change, the write speed will be stable. Tested on ARM64 device.
>
> Before:
>
> - dd if=/dev/zero of=/dev/sda bs=400K count=10485 (334 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=800K count=5242 (278 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=1600K count=2621 (204 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=2200K count=1906 (170 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=3000K count=1398 (150 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=4500K count=932 (139 MB/s)
>
> After:
>
> - dd if=/dev/zero of=/dev/sda bs=400K count=10485 (339 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=800K count=5242 (330 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=1600K count=2621 (332 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=2200K count=1906 (333 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=3000K count=1398 (333 MB/s)
> - dd if=/dev/zero of=/dev/sda bs=4500K count=932 (333 MB/s)
>
> Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace")
> Cc: stable@vger.kernel.org
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
next prev parent reply other threads:[~2024-05-24 12:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-21 11:49 [PATCH v5 1/2] filemap: add helper mapping_max_folio_size() Xu Yang
2024-05-21 11:49 ` [PATCH v5 2/2] iomap: fault in smaller chunks for non-large folio mappings Xu Yang
2024-05-24 8:03 ` Christoph Hellwig
2024-05-24 12:18 ` Matthew Wilcox [this message]
2024-05-21 14:22 ` [PATCH v5 1/2] filemap: add helper mapping_max_folio_size() Christian Brauner
2024-05-24 6:21 ` Ritesh Harjani
2024-05-24 8:03 ` Christoph Hellwig
2024-05-24 12:17 ` Matthew Wilcox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZlCFnlXPPUo_0mYX@casper.infradead.org \
--to=willy@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=brauner@kernel.org \
--cc=djwong@kernel.org \
--cc=jun.li@nxp.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-xfs@vger.kernel.org \
--cc=xu.yang_2@nxp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).