From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: semi-stable page writes
Date: Tue, 30 Oct 2012 13:40:37 -0700 [thread overview]
Message-ID: <20121030204037.GE19559@blackbox.djwong.org> (raw)
In-Reply-To: <20121029220122.GT29378@dastard>
On Tue, Oct 30, 2012 at 09:01:22AM +1100, Dave Chinner wrote:
> On Fri, Oct 26, 2012 at 03:19:09AM -0700, Darrick J. Wong wrote:
> > Hi everyone,
> >
> > Are people still annoyed about writes taking unexpectedly long amounts of tme
> > due to the stable page write patchset? I'm guessing yes...
>
> I haven't heard anyone except th elunatic fringe complain
> recently...
>
> > I'm close to posting a patchset that (a) gates the wait_on_page_writeback calls
> > on a flag that you can set in the bdi to indicate that you need stable writes
> > (which blk_integrity_register will set);
>
> I'd prefer stable pages by default (e.g. btrfs needs it for sane
> data crc calculations), with an option to turn it off.
>
> > (b) (ab)uses a page flag bit (PG_slab)
> > to indicate that a page is actually being sent out to disk hardware; and (c)
>
> I don't think you can do that. You can send slab allocated memory to
> disk (e.g. kmalloc()d memory) and XFS definitely does that for
> sub-page sized metadata. I'm pretty sure that means the PG_slab
> flag is not available for (ab)use in the IO path....
I gave up on PG_slab and declared my own PG_ bit. Unfortunately, atm I can't
remember which bit of code marks the page ptes so that they have to go back
through page_mkwrite, where we can trap the write. Hopefully for a shorter
duration.
Also, I was wondering -- is it possible to pursue a dual strategy? If we can
obtain a memory page without sleeping or causing any writeback, then use the
page as a bounce buffer. Otherwise, just wait like we do now. It looks as
though one could use __GFP_NORETRY | __GFP_NO_MEMALLOC to see if the allocator
can give out a page without having to run reclaim...?
--D
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
> --
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next prev parent reply other threads:[~2012-10-30 20:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 10:19 semi-stable page writes Darrick J. Wong
2012-10-27 1:35 ` [RFC PATCH 1/2] bdi: Create a flag to indicate that a backing device needs stable " Darrick J. Wong
2012-10-29 18:13 ` Jan Kara
2012-10-29 18:30 ` Jan Kara
2012-10-29 23:48 ` NeilBrown
2012-10-30 0:10 ` Jan Kara
2012-10-30 0:34 ` NeilBrown
2012-10-30 13:38 ` Jan Kara
2012-10-30 21:49 ` NeilBrown
2012-10-30 4:10 ` Martin K. Petersen
2012-10-30 4:48 ` NeilBrown
2012-10-30 12:19 ` Martin K. Petersen
2012-10-30 20:14 ` Darrick J. Wong
2012-10-30 22:14 ` NeilBrown
2012-10-30 23:58 ` Boaz Harrosh
2012-10-31 8:56 ` Darrick J. Wong
2012-10-31 11:56 ` Jan Kara
2012-10-31 19:36 ` Darrick J. Wong
2012-10-31 23:12 ` Boaz Harrosh
2012-11-01 5:51 ` Darrick J. Wong
2012-11-01 6:25 ` Boaz Harrosh
2012-11-01 8:59 ` Jan Kara
2012-11-01 17:24 ` Boaz Harrosh
2012-11-01 22:42 ` Jan Kara
2012-10-30 22:40 ` Boaz Harrosh
2012-10-27 1:36 ` [RFC PATCH 2/2] mm: Gate stable page writes on the bdi flag Darrick J. Wong
2012-10-29 18:28 ` Jan Kara
2012-10-31 8:58 ` Darrick J. Wong
2012-10-29 22:01 ` semi-stable page writes Dave Chinner
2012-10-30 1:00 ` Theodore Ts'o
2012-10-30 23:30 ` Dave Chinner
2012-10-31 11:45 ` Jan Kara
2012-10-30 20:40 ` Darrick J. Wong [this message]
2012-10-30 23:43 ` Dave Chinner
2012-10-31 9:05 ` Darrick J. Wong
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