From: "Theodore Ts'o" <firstname.lastname@example.org>
To: Dominique MARTINET <email@example.com>
Cc: "Matthew Wilcox (Oracle)" <firstname.lastname@example.org>,
Yu Kuai <email@example.com>,
Kent Overstreet <firstname.lastname@example.org>
Subject: Re: Major btrfs fiemap slowdown on file with many extents once in cache (RCU stalls?) (Was: [PATCH 1/3] filemap: Correct the conditions for marking a folio as accessed)
Date: Thu, 30 Jun 2022 10:37:58 -0400 [thread overview]
Message-ID: <Yr21RoL+ztf1W5Od@mit.edu> (raw)
On Thu, Jun 30, 2022 at 04:29:05PM +0900, Dominique MARTINET wrote:
> Hi Willy, linux-btrfs@vger,
> Matthew Wilcox (Oracle) wrote on Sun, Jun 19, 2022 at 04:11:41PM +0100:
> > We had an off-by-one error which meant that we never marked the first page
> > in a read as accessed. This was visible as a slowdown when re-reading
> > a file as pages were being evicted from cache too soon. In reviewing
> > this code, we noticed a second bug where a multi-page folio would be
> > marked as accessed multiple times when doing reads that were less than
> > the size of the folio.
> when debugging an unrelated issue (short reads on btrfs with io_uring
> and O_DIRECT), I noticed that my horrible big file copy speeds fell
> down from ~2GB/s (there's compression and lots of zeroes) to ~100MB/s
> the second time I was copying it with cp.
> I've taken a moment to bisect this and came down to this patch.
I think you may have forgotten to include the commit-id that was the
results of your bisect.... ?
next prev parent reply other threads:[~2022-06-30 14:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <email@example.com>
[not found] ` <firstname.lastname@example.org>
2022-06-30 7:29 ` Major btrfs fiemap slowdown on file with many extents once in cache (RCU stalls?) (Was: [PATCH 1/3] filemap: Correct the conditions for marking a folio as accessed) Dominique MARTINET
2022-06-30 14:37 ` Theodore Ts'o [this message]
2022-06-30 22:43 ` Dominique MARTINET
2022-07-01 1:55 ` Yu Kuai
2022-07-07 8:42 ` Dominique MARTINET
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