Messages in this thread | | | Date | Thu, 15 Sep 2005 03:13:09 +0530 | From | Dipankar Sarma <> | Subject | Re: VM balancing issues on 2.6.13: dentry cache not getting shrunk enough |
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On Wed, Sep 14, 2005 at 06:34:04PM -0300, Marcelo Tosatti wrote: > On Tue, Sep 13, 2005 at 02:17:52PM +0530, Bharata B Rao wrote: > > On Sun, Sep 11, 2005 at 11:16:36PM -0400, Theodore Ts'o wrote: > > > > Ted, > > > > I am sending two patches here. > > > > First is dentry_stats patch which collects some dcache statistics > > and puts it into /proc/meminfo. This patch provides information > > about how dentries are distributed in dcache slab pages, how many > > free and in use dentries are present in dentry_unused lru list and > > how prune_dcache() performs with respect to freeing the requested > > number of dentries. > > Hi Bharata, > > +void get_dstat_info(void) > +{ > + struct dentry *dentry; > + > + lru_dentry_stat.nr_total = lru_dentry_stat.nr_inuse = 0; > + lru_dentry_stat.nr_ref = lru_dentry_stat.nr_free = 0; > + > + spin_lock(&dcache_lock); > + list_for_each_entry(dentry, &dentry_unused, d_lru) { > + if (atomic_read(&dentry->d_count)) > + lru_dentry_stat.nr_inuse++; > > Dentries on dentry_unused list with d_count positive? Is that possible > at all? As far as my limited understanding goes, only dentries with zero > count can be part of the dentry_unused list.
That changed during the lock-free dcache implementation during 2.5. If we strictly update the lru list, we will have to acquire the dcache_lock in __d_lookup() on a successful lookup. So we did lazy-lru, leave the dentries with non-zero refcounts and clean them up later when we acquire dcache_lock for other purposes.
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