From: Andrew Morton <akpm@linux-foundation.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
Martin Bligh <mbligh@google.com>,
Michael Rubin <mrubin@google.com>,
Peter Zijlstra <peterz@infradead.org>, Jan Kara <jack@suse.cz>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] writeback: merge for_kupdate and !for_kupdate cases
Date: Mon, 12 Jul 2010 15:22:54 -0700 [thread overview]
Message-ID: <20100712152254.2071ba5f.akpm@linux-foundation.org> (raw)
In-Reply-To: <20100712155239.GC30222@localhost>
On Mon, 12 Jul 2010 23:52:39 +0800
Wu Fengguang <fengguang.wu@intel.com> wrote:
> > Also, I'd prefer that the
> > comments remain somewhat more descriptive of the circumstances that
> > we are operating under. Comments like "retry later to avoid blocking
> > writeback of other inodes" is far, far better than "retry later"
> > because it has "why" component that explains the reason for the
> > logic. You may remember why, but I sure won't in a few months time....
me2 (of course). This code is waaaay too complex to be scrimping on comments.
> Ah yes the comment is too simple. However the redirty_tail() is not to
> avoid blocking writeback of other inodes, but to avoid eating 100% CPU
> on busy retrying a dirty inode/page that cannot perform writeback for
> a while. (In theory redirty_tail() can still busy retry though, when
> there is only one single dirty inode.) So how about
>
> /*
> * somehow blocked: avoid busy retrying
> */
That's much too short. Expand on the "somehow" - provide an example,
describe the common/expected cause. Fully explain what the "busy"
retry _is_ and how it can come about.
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next prev parent reply other threads:[~2010-07-12 22:23 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-11 2:06 [PATCH 0/6] writeback cleanups and trivial fixes Wu Fengguang
2010-07-11 2:06 ` [PATCH 1/6] writeback: take account of NR_WRITEBACK_TEMP in balance_dirty_pages() Wu Fengguang
2010-07-12 21:52 ` Andrew Morton
2010-07-13 8:58 ` Miklos Szeredi
2010-07-15 14:50 ` Wu Fengguang
2010-07-11 2:06 ` [PATCH 2/6] writeback: reduce calls to global_page_state " Wu Fengguang
2010-07-26 15:19 ` Jan Kara
2010-07-27 3:59 ` Wu Fengguang
2010-07-27 9:12 ` Jan Kara
2010-07-28 2:04 ` Wu Fengguang
2010-08-03 14:55 ` Peter Zijlstra
2010-07-11 2:06 ` [PATCH 3/6] writeback: avoid unnecessary calculation of bdi dirty thresholds Wu Fengguang
2010-07-12 21:56 ` Andrew Morton
2010-07-15 14:55 ` Wu Fengguang
2010-07-19 21:35 ` Andrew Morton
2010-07-20 3:34 ` Wu Fengguang
2010-07-20 4:14 ` Andrew Morton
2010-08-03 15:03 ` Peter Zijlstra
2010-08-03 15:10 ` Wu Fengguang
2010-08-04 16:41 ` Wu Fengguang
2010-08-04 17:10 ` Peter Zijlstra
2010-07-11 2:07 ` [PATCH 4/6] writeback: dont redirty tail an inode with dirty pages Wu Fengguang
2010-07-12 2:01 ` Dave Chinner
2010-07-12 15:31 ` Wu Fengguang
2010-07-12 22:13 ` Andrew Morton
2010-07-15 15:35 ` Wu Fengguang
2010-07-11 2:07 ` [PATCH 5/6] writeback: fix queue_io() ordering Wu Fengguang
2010-07-12 22:15 ` Andrew Morton
2010-07-11 2:07 ` [PATCH 6/6] writeback: merge for_kupdate and !for_kupdate cases Wu Fengguang
2010-07-12 2:08 ` Dave Chinner
2010-07-12 15:52 ` Wu Fengguang
2010-07-12 22:06 ` Dave Chinner
2010-07-12 22:22 ` Andrew Morton [this message]
2010-08-05 16:01 ` Wu Fengguang
2010-07-11 2:44 ` [PATCH 0/6] writeback cleanups and trivial fixes Christoph Hellwig
2010-07-11 2:50 ` Wu Fengguang
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