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    SubjectRe: [patch 51/52] fs: per-zone dentry and inode LRU
    On Wed, Jun 30, 2010 at 08:09:37PM +1000, Dave Chinner wrote:
    > On Thu, Jun 24, 2010 at 01:03:03PM +1000, npiggin@suse.de wrote:
    > > Per-zone LRUs and shrinkers for dentry and inode caches.
    > >
    > > Signed-off-by: Nick Piggin <npiggin@suse.de>
    >
    > This destroys any notion we have of global LRU-ness of inode and
    > dentry caches, doesn't it?

    Yes.

    > Can you outline in more detail what sort
    > of reclaim pattern this results in. e.g. is a workload running on
    > a single node now effectively limited to a dentry/icache size within
    > the local node because of local node slab allocation and per-zone
    > reclaim?

    No, it will just make the vfs cache reclaim work similarly to
    pagecache reclaim. Reclaimers (kswapd) can work on node local
    memory; memory pressure in a particular zone can be targetted
    specifically instead of shrinking all zones until it is OK;
    zone reclaim will work properly for vfs caches; partitioning
    of workloads can be better.

    Workload on a single node can certainly still use up all global
    memory if that is how the policy is configured.

    Global LRU ordering is lost, but it is approximated when there
    is a global memory shortage by scanning a little from each zone
    head. When there is a local memory shortage it should be superior
    because that can be resolved without reclaiming so much memory.

    Thanks,
    Nick



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