On Thu, May 27, 2010 at 01:32:30PM -0700, Andrew Morton wrote: > On Tue, 25 May 2010 18:53:04 +1000 > Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > The inode unused list is currently a global LRU. This does not match > > the other global filesystem cache - the dentry cache - which uses > > per-superblock LRU lists. Hence we have related filesystem object > > types using different LRU reclaimatin schemes. > > > > To enable a per-superblock filesystem cache shrinker, both of these > > caches need to have per-sb unused object LRU lists. Hence this patch > > converts the global inode LRU to per-sb LRUs. > > > > The patch only does rudimentary per-sb propotioning in the shrinker > > infrastructure, as this gets removed when the per-sb shrinker > > callouts are introduced later on. > > > > ... > > > > + list_move(&inode->i_list, &inode->i_sb->s_inode_lru); > > It's a shape that s_inode_lru is still protected by inode_lock. One > day we're going to get in trouble over that lock. Migrating to a > per-sb lock would be logical and might help. > > Did you look into this? Yes, I have. Yes, it's possible. It's solving a different problem, so I figured it can be done in a different patch set. > I expect we'd end up taking both inode_lock > and the new sb->lru_lock in several places, which wouldn't be of any > help, at least in the interim. Long-term, the locking for > fs-writeback.c should move to the per-superblock one also, at which > time this problem largely goes away I think. Unfortunately the > writeback inode lists got moved into the backing_dev_info, whcih messes > things up a bit. *nod* > > > inodes_stat.nr_unused--; > > + inode->i_sb->s_nr_inodes_unused--; > > It's regrettable to be counting the same thing twice. Did you look > into removing (or no longer using) inodes_stat.nr_unused? Sort of. The complexity is the stats are userspace visible, so they can't just be removed. Replacing the current stats means that when they are read from /proc we would need to walk all the superblocks to aggregate them. The bit I haven't looked at yet is whether walking superblocks is allowed in a proc handler. So in the mean time, I just copied what was done for the dentry_stats. If it's ok to do this walk, then we can change both the dentry and inode stats at the same time. > > + /* Now, we reclaim unused dentrins with fairness. > > May as well fix the typo while we're there. > > Please review all these comments to ensure that they are still accurate > and complete. Will do. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
