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 17:22:49 -0800 [thread overview]
Message-ID: <CAHk-=wj0pXsngjWKw5p3oTvwkNnT2DyoZWqPB+-wBY+BGTQ96w@mail.gmail.com> (raw)
In-Reply-To: <1c93194a-ed91-c3aa-deb5-a3394805defb@kernel.dk>
On Wed, Dec 11, 2019 at 5:11 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> 15K is likely too slow to really show an issue, I'm afraid. The 970
> is no slouch, but your crypt setup will likely hamper it a lot. You
> don't have a non-encrypted partition on it?
No. I normally don't need all that much disk, so I've never upgraded
my ssd from the 512G size.
Which means that it's actually half full or so, and I never felt like
"I should keep an unencrypted partition for IO testing", since I don't
generally _do_ any IO testing.
I can get my load up with "numjobs=8" and get my iops up to the 100k
range, though.
But kswapd doesn't much seem to care, the CPU percentage actually does
_down_ to 0.39% when I try that. Probably simply because now my CPU's
are busy, so they are running at 4.7Ghz instead of the 800Mhz "mostly
idle" state ...
I guess I should be happy. It does mean that the situation you see
isn't exactly the normal case. I understand why you want to do the
non-cached case, but the case I think it the worrisome one is the
regular buffered one, so that's what I'm testing (not even trying the
noaccess patches).
So from your report I went "uhhuh, that sounds like a bug". And it
appears that it largely isn't - you're seeing it because of pushing
the IO subsystem by another order of magnitude (and then I agree that
"under those kinds of IO loads, caching just won't help")
Linus
next prev parent reply other threads:[~2019-12-12 1:23 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 15:29 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 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 17:56 ` Jens Axboe
2019-12-11 19:14 ` Linus Torvalds
2019-12-11 19:34 ` Jens Axboe
2019-12-11 20:03 ` Linus Torvalds
2019-12-11 20:08 ` Jens Axboe
2019-12-11 20:18 ` Linus Torvalds
2019-12-11 23:41 ` Jens Axboe
2019-12-12 1:08 ` Linus Torvalds
2019-12-12 1:11 ` Jens Axboe
2019-12-12 1:22 ` Linus Torvalds [this message]
2019-12-12 1:29 ` Jens Axboe
2019-12-12 1:41 ` Linus Torvalds
2019-12-12 1:56 ` Matthew Wilcox
2019-12-12 2:47 ` Linus Torvalds
2019-12-12 17:52 ` Matthew Wilcox
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 1:09 ` 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
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