Re: [patch 6/9] mm + fs: store shadow entries in page cache

[Johannes Weiner <hannes@cmpxchg.org>]

On Tue, Nov 26, 2013 at 11:20:53AM +0100, Peter Zijlstra wrote:
> On Tue, Nov 26, 2013 at 10:17:16AM +1100, Dave Chinner wrote:
> > void truncate_inode_pages_final(struct address_space *mapping)
> > {
> > 	mapping_set_exiting(mapping);
> > 	if (inode->i_data.nrpages || inode->i_data.nrshadows) {
> > 		/*
> > 		 * spinlock barrier to ensure all modifications are
> > 		 * complete before we do the final truncate
> > 		 */
> > 		spin_lock_irq(&mapping->tree_lock);
> > 		spin_unlock_irq(&mapping->tree_lock);
> 
> 	spin_unlock_wait() ?
> 
> Its cheaper, but prone to starvation; its typically useful when you're
> waiting for the last owner to go away and know there won't be any new
> ones around.

The other side is reclaim plucking pages one-by-one from the address
space in LRU order.  It'd be preferable to not starve the truncation
side, because it is much more efficient at getting rid of those pages.

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