From: Minchan Kim <minchan.kim@gmail.com>
To: Johannes Weiner <jweiner@redhat.com>
Cc: Andrew Morton <akpm@google.com>, Mel Gorman <mgorman@suse.de>,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
Rik van Riel <riel@redhat.com>,
Chris Mason <chris.mason@oracle.com>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
xfs@oss.sgi.com, linux-btrfs@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch 2/2/4] mm: try to distribute dirty pages fairly across zones
Date: Thu, 29 Sep 2011 03:09:07 +0900 [thread overview]
Message-ID: <20110928180907.GD1696@barrios-desktop> (raw)
In-Reply-To: <20110928071154.GA23535@redhat.com>
On Wed, Sep 28, 2011 at 09:11:54AM +0200, Johannes Weiner wrote:
> On Wed, Sep 28, 2011 at 02:56:40PM +0900, Minchan Kim wrote:
> > On Fri, Sep 23, 2011 at 04:42:48PM +0200, Johannes Weiner wrote:
> > > The maximum number of dirty pages that exist in the system at any time
> > > is determined by a number of pages considered dirtyable and a
> > > user-configured percentage of those, or an absolute number in bytes.
> >
> > It's explanation of old approach.
>
> What do you mean? This does not change with this patch. We still
> have a number of dirtyable pages and a limit that is applied
> relatively to this number.
>
> > > This number of dirtyable pages is the sum of memory provided by all
> > > the zones in the system minus their lowmem reserves and high
> > > watermarks, so that the system can retain a healthy number of free
> > > pages without having to reclaim dirty pages.
> >
> > It's a explanation of new approach.
>
> Same here, this aspect is also not changed with this patch!
>
> > > But there is a flaw in that we have a zoned page allocator which does
> > > not care about the global state but rather the state of individual
> > > memory zones. And right now there is nothing that prevents one zone
> > > from filling up with dirty pages while other zones are spared, which
> > > frequently leads to situations where kswapd, in order to restore the
> > > watermark of free pages, does indeed have to write pages from that
> > > zone's LRU list. This can interfere so badly with IO from the flusher
> > > threads that major filesystems (btrfs, xfs, ext4) mostly ignore write
> > > requests from reclaim already, taking away the VM's only possibility
> > > to keep such a zone balanced, aside from hoping the flushers will soon
> > > clean pages from that zone.
> >
> > It's a explanation of old approach, again!
> > Shoudn't we move above phrase of new approach into below?
>
> Everything above describes the current behaviour (at the point of this
> patch, so respecting lowmem_reserve e.g. is part of the current
> behaviour by now) and its problems. And below follows a description
> of how the patch tries to fix it.
It seems that it's not a good choice to use "old" and "new" terms.
Hannes, please ignore, it's not a biggie.
--
Kind regards,
Minchan Kim
next prev parent reply other threads:[~2011-09-28 18:09 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 13:45 [patch 0/4] 50% faster writing to your USB drive!* Johannes Weiner
2011-09-20 13:45 ` [patch 1/4] mm: exclude reserved pages from dirtyable memory Johannes Weiner
2011-09-20 15:21 ` Rik van Riel
2011-09-21 14:04 ` Mel Gorman
2011-09-21 15:03 ` Mel Gorman
2011-09-22 9:03 ` Johannes Weiner
2011-09-22 10:54 ` Mel Gorman
2011-09-23 14:38 ` [patch 1/4 v2] " Johannes Weiner
2011-09-28 4:55 ` Minchan Kim
2011-09-28 7:50 ` Johannes Weiner
2011-09-28 18:35 ` Minchan Kim
2011-09-20 13:45 ` [patch 2/4] mm: writeback: distribute write pages across allowable zones Johannes Weiner
2011-09-20 18:36 ` Rik van Riel
2011-09-21 11:04 ` Shaohua Li
2011-09-21 13:35 ` Johannes Weiner
2011-09-21 14:30 ` Mel Gorman
2011-09-21 23:02 ` Andrew Morton
2011-09-22 8:52 ` Johannes Weiner
2011-09-23 14:41 ` [patch 1/2/4] mm: writeback: cleanups in preparation for per-zone dirty limits Johannes Weiner
2011-09-28 5:57 ` Minchan Kim
2011-09-28 9:27 ` Mel Gorman
2011-09-23 14:42 ` [patch 2/2/4] mm: try to distribute dirty pages fairly across zones Johannes Weiner
2011-09-28 5:56 ` Minchan Kim
2011-09-28 7:11 ` Johannes Weiner
2011-09-28 18:09 ` Minchan Kim [this message]
2011-09-28 9:36 ` Mel Gorman
2011-09-20 13:45 ` [patch 3/4] mm: filemap: pass __GFP_WRITE from grab_cache_page_write_begin() Johannes Weiner
2011-09-20 14:25 ` Christoph Hellwig
2011-09-20 18:38 ` Rik van Riel
2011-09-20 18:40 ` Christoph Hellwig
2011-09-21 14:09 ` Johannes Weiner
2011-09-20 18:40 ` Rik van Riel
2011-09-21 14:34 ` Mel Gorman
2011-09-28 6:02 ` Minchan Kim
2011-09-20 13:45 ` [patch 4/4] Btrfs: pass __GFP_WRITE for buffered write page allocations Johannes Weiner
2011-09-20 13:56 ` Johannes Weiner
2011-09-20 14:09 ` Josef Bacik
2011-09-20 14:14 ` Johannes Weiner
2011-09-20 18:41 ` Rik van Riel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110928180907.GD1696@barrios-desktop \
--to=minchan.kim@gmail.com \
--cc=adilger.kernel@dilger.ca \
--cc=akpm@google.com \
--cc=akpm@linux-foundation.org \
--cc=chris.mason@oracle.com \
--cc=david@fromorbit.com \
--cc=fengguang.wu@intel.com \
--cc=hch@infradead.org \
--cc=jack@suse.cz \
--cc=jweiner@redhat.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=riel@redhat.com \
--cc=tytso@mit.edu \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).