Messages in this thread | | | Date | Thu, 15 Sep 2005 09:58:38 +0530 | From | Bharata B Rao <> | 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: > > > On Sun, Sep 11, 2005 at 05:30:46PM +0530, Dipankar Sarma wrote: > > > > Do you have the /proc/sys/fs/dentry-state output when such lowmem > > > > shortage happens ? > > > > > > Not yet, but the situation occurs on my laptop about 2 or 3 times > > > (when I'm not travelling and so it doesn't get rebooted). So > > > reproducing it isn't utterly trivial, but it's does happen often > > > enough that it should be possible to get the necessary data. > > > > > > > This is a problem that Bharata has been investigating at the moment. > > > > But he hasn't seen anything that can't be cured by a small memory > > > > pressure - IOW, dentries do get freed under memory pressure. So > > > > your case might be very useful. Bharata is maintaing an instrumentation > > > > patch to collect more information and an alternative dentry aging patch > > > > (using rbtree). Perhaps you could try with those. > > > > > > Send it to me, and I'd be happy to try either the instrumentation > > > patch or the dentry aging patch. > > > > > > > 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.
As Dipankar mentioned, its now possible to have positive d_count dentires on unused_list. BTW I think we need a better way to get this data than going through the entire unused_list linearly, which might not be scalable with huge number of dentries.
> > + if (dentry->d_flags & DCACHE_REFERENCED) > + lru_dentry_stat.nr_ref++; > + } > > > @@ -393,6 +430,9 @@ static inline void prune_one_dentry(stru > > static void prune_dcache(int count) > { > + int nr_requested = count; > + int nr_freed = 0; > + > spin_lock(&dcache_lock); > for (; count ; count--) { > struct dentry *dentry; > @@ -427,8 +467,13 @@ static void prune_dcache(int count) > continue; > } > prune_one_dentry(dentry); > + nr_freed++; > } > spin_unlock(&dcache_lock); > + spin_lock(&prune_dcache_lock); > + lru_dentry_stat.dprune_req = nr_requested; > + lru_dentry_stat.dprune_freed = nr_freed; > > Don't you mean "+=" ?
No. Actually here I am capturing the number of dentries freed per invocation of prune_dcache.
Regards, Bharata. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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