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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: 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>, Chris Mason <clm@fb.com>,
	Dave Chinner <david@fromorbit.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCHSET v3 0/5] Support for RWF_UNCACHED
Date: Wed, 11 Dec 2019 17:49:57 -0800	[thread overview]
Message-ID: <CAHk-=wjkpRnqDfcR1h2NyCN7Ka9T0DcHgBL=e9pVvYG2u0APdQ@mail.gmail.com> (raw)
In-Reply-To: <6e2ca035-0e06-1def-5ea9-90a7466b2d49@kernel.dk>

On Wed, Dec 11, 2019 at 5:41 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> So now I'm even more puzzled why your (desktop?) doesn't show it, it
> must be more potent than my x1 laptop. But for me, the laptop and 2
> socket test box show EXACTLY the same behavior, laptop is just too slow
> to make it really pathological.

I see the exact same thing.

And now, go do "perf record -a sleep 100" while this is going on, to
see the big picture.

Suddenly that number is a lot smaller. Because the kswapd cost is less
than 10% of one cpu, and the xas_create is 30% of that. IOW, it's not
all that dominant until you zoom in on it. Considering the amount of
IO going on, it's kind of understandable.

But as mentioned, it does look like something that should be fixed.
Maybe it's even something where it's a bad XArray case? Willy?

              Linus

  reply	other threads:[~2019-12-12  1:50 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 [this message]
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
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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