From: Christoph Hellwig <hch@infradead.org>
To: Chris Mason <clm@fb.com>
Cc: Dave Chinner <david@fromorbit.com>, Jens Axboe <axboe@kernel.dk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCHSET v3 0/5] Support for RWF_UNCACHED
Date: Tue, 7 Jan 2020 09:42:02 -0800 [thread overview]
Message-ID: <20200107174202.GA8938@infradead.org> (raw)
In-Reply-To: <C08B7F86-C3D6-47C6-AB17-6F234EA33687@fb.com>
On Fri, Dec 13, 2019 at 01:32:10AM +0000, Chris Mason wrote:
> They just have different tradeoffs. O_DIRECT actively blows away caches
> and can also force writes during reads, making RWF_UNCACHED a more
> natural fit for some applications. There are fewer surprises, and some
> services are willing to pay for flexibility with a memcpy. In general,
> they still want to do some cache management because it reduces p90+
> latencies across the board, and gives them more control over which pages
> stay in cache.
We can always have a variant of O_DIRECT that doesn't do that and
instead check if data was in the cache and then also copy / from to
it in that case. I need some time to actually look through this series,
so it might be pretty similar to the implementation, but if defined
the right way it could be concurrent for at least the fast path of no
cached pages.
next prev parent reply other threads:[~2020-01-07 17:42 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 15:29 [PATCHSET v3 0/5] Support for RWF_UNCACHED Jens Axboe
2019-12-11 15:29 ` [PATCH 1/5] fs: add read support " Jens Axboe
2019-12-11 15:29 ` [PATCH 2/5] mm: make generic_perform_write() take a struct kiocb Jens Axboe
2019-12-11 15:29 ` [PATCH 3/5] mm: make buffered writes work with RWF_UNCACHED Jens Axboe
2019-12-11 15:29 ` [PATCH 4/5] iomap: pass in the write_begin/write_end flags to iomap_actor Jens Axboe
2019-12-11 17:19 ` Linus Torvalds
2019-12-11 17:19 ` Linus Torvalds
2019-12-11 15:29 ` [PATCH 5/5] iomap: support RWF_UNCACHED for buffered writes Jens Axboe
2019-12-11 17:19 ` Matthew Wilcox
2019-12-11 18:05 ` Jens Axboe
2019-12-12 22:34 ` Dave Chinner
2019-12-13 0:54 ` Jens Axboe
2019-12-13 0:57 ` Jens Axboe
2019-12-16 4:17 ` Dave Chinner
2019-12-17 14:31 ` Jens Axboe
2019-12-18 0:49 ` Dave Chinner
2019-12-18 1:01 ` Jens Axboe
2019-12-11 17:37 ` [PATCHSET v3 0/5] Support for RWF_UNCACHED Linus Torvalds
2019-12-11 17:37 ` Linus Torvalds
2019-12-11 17:56 ` Jens Axboe
2019-12-11 19:14 ` Linus Torvalds
2019-12-11 19:14 ` Linus Torvalds
2019-12-11 19:34 ` Jens Axboe
2019-12-11 20:03 ` Linus Torvalds
2019-12-11 20:03 ` Linus Torvalds
2019-12-11 20:08 ` Jens Axboe
2019-12-11 20:18 ` Linus Torvalds
2019-12-11 20:18 ` Linus Torvalds
2019-12-11 21:04 ` Johannes Weiner
2019-12-12 1:30 ` Jens Axboe
2019-12-11 23:41 ` Jens Axboe
2019-12-12 1:08 ` Linus Torvalds
2019-12-12 1:08 ` Linus Torvalds
2019-12-12 1:11 ` Jens Axboe
2019-12-12 1:22 ` Linus Torvalds
2019-12-12 1:22 ` Linus Torvalds
2019-12-12 1:29 ` Jens Axboe
2019-12-12 1:41 ` Linus Torvalds
2019-12-12 1:41 ` Linus Torvalds
2019-12-12 1:56 ` Matthew Wilcox
2019-12-12 2:47 ` Linus Torvalds
2019-12-12 2:47 ` Linus Torvalds
2019-12-12 17:52 ` Matthew Wilcox
2019-12-12 18:29 ` Linus Torvalds
2019-12-12 18:29 ` Linus Torvalds
2019-12-12 20:05 ` Matthew Wilcox
2019-12-12 1:41 ` Jens Axboe
2019-12-12 1:49 ` Linus Torvalds
2019-12-12 1:49 ` Linus Torvalds
2019-12-12 1:09 ` Jens Axboe
2019-12-12 2:03 ` Jens Axboe
2019-12-12 2:10 ` Jens Axboe
2019-12-12 2:21 ` Matthew Wilcox
2019-12-12 2:38 ` Jens Axboe
2019-12-12 22:18 ` Dave Chinner
2019-12-13 1:32 ` Chris Mason
2020-01-07 17:42 ` Christoph Hellwig [this message]
2020-01-08 14:09 ` Chris Mason
2020-02-01 10:33 ` Andres Freund
2019-12-11 20:43 ` Matthew Wilcox
2019-12-11 20:04 ` Jens Axboe
2019-12-12 10:44 ` Martin Steigerwald
2019-12-12 15:16 ` Jens Axboe
2019-12-12 21:45 ` Martin Steigerwald
2019-12-12 22:15 ` Jens Axboe
2019-12-12 22:18 ` Linus Torvalds
2019-12-12 22:18 ` Linus Torvalds
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