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    SubjectRe: [PATCH 3/5] superblock: introduce per-sb cache shrinker infrastructure
    On Thu, May 27, 2010 at 02:07:04PM +1000, Dave Chinner wrote:
    > On Thu, May 27, 2010 at 12:19:05PM +1000, Nick Piggin wrote:
    > > On Thu, May 27, 2010 at 09:12:14AM +1000, Dave Chinner wrote:
    > > > On Thu, May 27, 2010 at 02:41:16AM +1000, Nick Piggin wrote:
    > > > > > + count = ((sb->s_nr_dentry_unused + sb->s_nr_inodes_unused) / 100)
    > > > > > + * sysctl_vfs_cache_pressure;
    > > > >
    > > > > Do you think truncating in the divisions is at all a problem? It
    > > > > probably doesn't matter much I suppose.
    > > >
    > > > Same code as currently exists. IIRC, the reasoning is that if we've
    > > > got less that 100 objects to reclaim, then we're unlikely to be able
    > > > to free up any memory from the caches, anyway.
    > >
    > > Yeah, which is why I stop short of saying you should change it in
    > > this patch.
    > >
    > > But I think we should ensure things can get reclaimed eventually.
    > > 100 objects could be 100 slabs, which could be anything from
    > > half a meg to half a dozen. Multiplied by each of the caches.
    > > Could be significant in small systems.
    >
    > True, but usually there are busy objects in the dentry and inode
    > slabs, so it shouldn't be a significant issue. We can probably
    > address such problems if they can be demonstrated to be an issue in
    > a separate patch set....

    I didn't want to say it is a problem with your patchset, I just
    thought of it when reviewing.


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