On Wed, 2012-05-02 at 15:06 -0700, Tim Chen wrote: > The following patch detects when inodes and dentries cache are really > low in free entries, and skip reclamation of memory from them when it is > futile to do so. We only resume reclaiming memory from inodes and > dentries cache when we have a reasonable amount of memory there. > This avoided us bottlenecking on sb_lock to do useless memory > reclamation. > > I assume that it is okay to check super block's number of free objects > content without sb_lock as we are holding shrinker list's read lock. The > shrinker is still registered so super block is not yet deactivated which > requires shrinker un-registration. It will be great if Al can help to > comment on whether this assumption is okay. > > In a test scenario where page cache is putting heavy pressure on memory > usage with large number of processes, we saw very heavy contention on > the sb_lock to get free pages as seen in the following profile. The > patch helped to reduce the runtime by almost a factor of 4. > > 62.81% cp [kernel.kallsyms] [k] _raw_spin_lock > | > --- _raw_spin_lock > | > |--45.19%-- grab_super_passive > | prune_super > | shrink_slab > | do_try_to_free_pages > | try_to_free_pages > | __alloc_pages_nodemask > | alloc_pages_current > > > Tim Hi Al, Want to ping you again to see what your thoughts are on this patch I've sent a week ago. Thanks. Tim -- 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
