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    SubjectRe: [PATCH 1/5] inode: Make unused inode LRU per superblock
    On Fri, May 28, 2010 at 08:54:18AM +1000, Dave Chinner wrote:
    > 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@fromorbit.com> wrote:
    > >
    > > > From: Dave Chinner <dchinner@redhat.com>
    > > >
    > > > 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.

    It almost all goes away in my inode lock splitup patches. Inode lru
    and dirty lists were the last things protected by the global lock
    there.

    I am actually going to do per-zone lrus for these guys and per-zone
    locks (which is actually better than per-sb because it gives NUMA
    scalability within a single sb).

    The dirty/writeback lists should probably be per-bdi locked.




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