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 17:41:16 -0800 [thread overview]
Message-ID: <CAHk-=whtf0-f5wCcSAj=oTK2TEaesF43UdHnPyvgE9X1EuwvBw@mail.gmail.com> (raw)
In-Reply-To: <d8a8ea42-7f76-926c-ae9a-d49b11578153@kernel.dk>
On Wed, Dec 11, 2019 at 5:29 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> I'd very much argue that it IS a bug, maybe just doesn't show on your
> system.
Oh, I agree. But I also understand why people hadn't noticed, and I
don't think it's all that critical - because if you do 1M iops cached,
you're doing something really really strange.
I too can see xas_create using 30% CPU time, but that's when I do a
perf record on just kswapd - and when I actually look at it on a
system level, it looks nowhere near that bad.
So I think people should look at this. Part of it might be for Willy:
does that xas_create() need to be that expensive? I hate how "perf"
callchains work, but it does look like it is probably
page_cache_delete -> xas_store -> xas_create that is the bulk of the
cost there.
Replacing the real page with the shadow entry shouldn't be that big of
a deal, I would really hope.
Willy, that used to be a __radix_tree_lookup -> __radix_tree_replace
thing, is there perhaps some simple optmization that could be done on
the XArray case here?
Linus
next prev parent reply other threads:[~2019-12-12 1:41 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 [this message]
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
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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