linux-kernel - Re: [PATCH 0/11] Per-bdi writeback flusher threads v8

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Date:	Wed, 27 May 2009 21:15:24 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Theodore Tso <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
	akpm@...ux-foundation.org, jack@...e.cz,
	yanmin_zhang@...ux.intel.com, richard@....demon.co.uk,
	damien.wyart@...e.fr
Subject: Re: [PATCH 0/11] Per-bdi writeback flusher threads v8

On Wed, May 27 2009, Jens Axboe wrote:
> On Wed, May 27 2009, Theodore Tso wrote:
> > On Wed, May 27, 2009 at 01:53:53PM -0400, Theodore Tso wrote:
> > > On Wed, May 27, 2009 at 10:47:54AM -0400, Theodore Tso wrote:
> > > > 
> > > > I'll retry the test with your stock writeback-v8 git branch w/o any
> > > > ext4 patches planned the next mere window mainline to see if I get the
> > > > same soft lockup, but I thought I should give you an early heads up.
> > > 
> > > Confirmed.  I had to run fsstress twice, but I was able to trigger a
> > > soft hangup with just the per-bdi v8 patches using ext4.
> > 
> > As you requested, here's the .config file which I used.  This was on a
> > Lenovo S10 (N270 Atom dual-core CPU, 1.5 gigs of memory, 5400 rpm hdd).
> 
> If you have time, can you rerun with this little patch? It moves the
> super sync to a separate thread. Thanks!
> 
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index f71588c..8b30f29 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -218,10 +218,14 @@ static __init int bdi_class_init(void)
>  }
>  postcore_initcall(bdi_class_init);
>  
> +static int bdi_sync_supers(void *unused);
> +
>  static int __init default_bdi_init(void)
>  {
>  	int err;
>  
> +	kthread_run(bdi_sync_supers, NULL, "bdi-super");
> +
>  	err = bdi_init(&default_backing_dev_info);
>  	if (!err)
>  		bdi_register(&default_backing_dev_info, NULL, "default");
> @@ -412,6 +416,20 @@ static void bdi_flush_io(struct backing_dev_info *bdi)
>  	generic_sync_bdi_inodes(NULL, &wbc);
>  }
>  
> +static int bdi_sync_supers(void *unused)
> +{
> +	while (!kthread_should_stop()) {
> +		schedule_timeout(dirty_expire_interval * 10);

Woops, that should be

                schedule_timeout(msecs_to_jiffies(dirty_expire_interval * 10));

of course, otherwise we sync quite a lot :-)

-- 
Jens Axboe

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