[PATCH 1/5] xfs: use per-filesystem I/O completion workqueues

[Dave Chinner]

On Tue, Feb 07, 2012 at 01:10:38PM -0500, Christoph Hellwig wrote:
> The new concurrency managed workqueues are cheap enough that we can create
> per-filesystem instead of global workqueues.  This allows us to remove the
> trylock or defer scheme on the ilock, which is not helpful once we have
> outstanding log reservations until finishing a size update.

Agreed.

And it removes some of the issues with dependencies between
filesystems like loopback mounted XFS-on-XFS filesystems, though to
fix them completely we also need per-filesystem log workqueues. Is
it worth just converting that one as well in this patch just to
remove all global work queues?


> Signed-off-by: Christoph Hellwig <hch at lst.de>

....
> +STATIC int
> +xfs_init_mount_workqueues(
> +	struct xfs_mount	*mp)
> +{
> +#define XFS_WQ_NAME_LEN		512
> +	char			name[XFS_WQ_NAME_LEN];
> +
> +	snprintf(name, XFS_WQ_NAME_LEN, "xfs-data/%s", mp->m_fsname);
> +	mp->m_data_workqueue = alloc_workqueue(name, WQ_MEM_RECLAIM, 1);
> +	if (!mp->m_data_workqueue)
> +		goto out;

As of b196be8 ("workqueue: make alloc_workqueue() take printf fmt and
args for name"), this dance is not necessary. somethign like:

	mp->m_data_workqueue = alloc_workqueue(name, WQ_MEM_RECLAIM, 1,
						"xfs-data/%s", mp->m_fsname);

will work just fine.

Also, I thin kwe want significant parallelism on this workqueue -
having an inode block on an ilock shoul dnot stop us from processing
other ioends in the same fs....

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com