From: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
To: Jens Axboe <axboe@kernel.dk>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-block@vger.kernel.org
Cc: willy@infradead.org, clm@fb.com, torvalds@linux-foundation.org,
david@fromorbit.com
Subject: Re: [PATCH 1/6] fs: add read support for RWF_UNCACHED
Date: Tue, 17 Dec 2019 16:16:40 +0100 [thread overview]
Message-ID: <1d0bf482-8786-00b7-310d-4de38607786d@cloud.ionos.com> (raw)
In-Reply-To: <20191217143948.26380-2-axboe@kernel.dk>
On 12/17/19 3:39 PM, Jens Axboe wrote:
> If RWF_UNCACHED is set for io_uring (or preadv2(2)), we'll use private
> pages for the buffered reads. These pages will never be inserted into
> the page cache, and they are simply droped when we have done the copy at
> the end of IO.
>
> If pages in the read range are already in the page cache, then use those
> for just copying the data instead of starting IO on private pages.
>
> A previous solution used the page cache even for non-cached ranges, but
> the cost of doing so was too high. Removing nodes at the end is
> expensive, even with LRU bypass. On top of that, repeatedly
> instantiating new xarray nodes is very costly, as it needs to memset 576
> bytes of data, and freeing said nodes involve an RCU call per node as
> well. All that adds up, making uncached somewhat slower than O_DIRECT.
>
> With the current*solition*, we're basically at O_DIRECT levels of
Maybe it is 'solution' here.
Thanks,
Guoqing
next prev parent reply other threads:[~2019-12-17 15:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 14:39 [PATCHSET v5 0/6] Support for RWF_UNCACHED Jens Axboe
2019-12-17 14:39 ` [PATCH 1/6] fs: add read support " Jens Axboe
2019-12-17 15:16 ` Guoqing Jiang [this message]
2019-12-17 16:42 ` Jens Axboe
2019-12-17 15:57 ` Matthew Wilcox
2019-12-17 16:41 ` Jens Axboe
2019-12-18 3:17 ` Dave Chinner
2019-12-17 14:39 ` [PATCH 2/6] mm: make generic_perform_write() take a struct kiocb Jens Axboe
2019-12-17 14:39 ` [PATCH 3/6] mm: make buffered writes work with RWF_UNCACHED Jens Axboe
2019-12-17 14:39 ` [PATCH 4/6] iomap: add struct iomap_ctx Jens Axboe
2019-12-17 19:39 ` Linus Torvalds
2019-12-17 19:39 ` Linus Torvalds
2019-12-17 20:26 ` Linus Torvalds
2019-12-17 20:26 ` Linus Torvalds
2019-12-18 0:15 ` Jens Axboe
2019-12-18 1:25 ` Darrick J. Wong
2019-12-26 9:49 ` [iomap] 5c6f67c138: WARNING:at_fs/iomap/buffered-io.c:#iomap_readpages kernel test robot
2019-12-26 9:49 ` kernel test robot
2019-12-17 14:39 ` [PATCH 5/6] iomap: support RWF_UNCACHED for buffered writes Jens Axboe
2019-12-18 1:52 ` Darrick J. Wong
2019-12-18 3:18 ` Jens Axboe
2019-12-18 4:15 ` Darrick J. Wong
2019-12-17 14:39 ` [PATCH 6/6] xfs: don't do delayed allocations for uncached " Jens Axboe
2019-12-18 1:57 ` Darrick J. Wong
2019-12-18 1:57 ` Darrick J. Wong
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=1d0bf482-8786-00b7-310d-4de38607786d@cloud.ionos.com \
--to=guoqing.jiang@cloud.ionos.com \
--cc=axboe@kernel.dk \
--cc=clm@fb.com \
--cc=david@fromorbit.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=torvalds@linux-foundation.org \
--cc=willy@infradead.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.