On Sun, Nov 20, 2011 at 02:23:34AM -0500, Christoph Hellwig wrote:
> If we are doing synchronous inode reclaim we block the VM from making
> progress in memory reclaim. So if we encouter a flush locked inode
> make sure we force out all delayed buffers ASAP to speed up the wait
> for it to be unlocked. Without this we can get hangs of up to 30
> seconds during workloads hitting synchronous inode reclaim.
I don't think we need to push out all delayed buffers - that's an
awfully big sledge hammer to get a single buffer moving. Indeed, we
already have a mechanism for dealing with this problem -
xfs_buf_delwri_promote() - when we hit it during AIL flushing.
IOWs, we only need to promote the buffer the inode sits in and kick
xfsbufd. that is, something like:
bp = xfs_incore(ip->i_mount->m_ddev_targp, iip->ili_format.ilf_blkno,
iip->ili_format.ilf_len, XBF_TRYLOCK);
if (bp && XFS_BUF_ISDELAYWRITE(bp)) {
xfs_buf_delwri_promote(bp);
wake_up_process(mp->m_ddev_targp->bt_task);
}
if (bp)
xfs_buf_relse(bp);
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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