Re: regression in page writeback

From: Wu Fengguang <fengguang.wu@intel.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>,
	Chris Mason <chris.mason@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	"Li, Shaohua" <shaohua.li@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"richard@rsk.demon.co.uk" <richard@rsk.demon.co.uk>,
	"jens.axboe@oracle.com" <jens.axboe@oracle.com>
Subject: Re: regression in page writeback
Date: Tue, 29 Sep 2009 10:32:27 +0800	[thread overview]
Message-ID: <20090929023227.GA20153@localhost> (raw)
In-Reply-To: <20090928130804.GA25880@infradead.org>

On Mon, Sep 28, 2009 at 09:08:04PM +0800, Christoph Hellwig wrote:
> On Mon, Sep 28, 2009 at 03:15:07PM +0800, Wu Fengguang wrote:
> > +		if (!PageActive(page))
> > +			SetPageReclaim(page);
> > +		err = mapping->a_ops->writepage(page, wbc);
> > +		if (err < 0)
> > +			handle_write_error(mapping, page, res);
> > +		if (err == AOP_WRITEPAGE_ACTIVATE) {
> > +			ClearPageReclaim(page);
> > +			res = PAGE_ACTIVATE;
> > +			break;
> > +		}
> 
> This should help a bit for XFS as it historically does multi-page
> writeouts from ->writepages (and apprently btrfs that added some

->writepage ?

> write-around recently?) but not those brave filesystems only
> implementing the multi-page writeout from writepages as designed.

Thanks.  Just tried write_cache_pages(), looks simple. Need to further
convert all aops->writepages to support lumpy pageout :)

> But really, the best would be to leave the writeout to the flusher
> threads and just reclaim the clean pages from the VM.

Yup, that's much larger behavior change, and could be pursued as a
long term goal.

Thanks,
Fengguang