Re: [patch] voluntary-preempt-2.6.8.1-P9

[Lee Revell <rlrevell@joe-job.com>]

On Sat, 2004-08-28 at 03:37, Ingo Molnar wrote:
> * Lee Revell <rlrevell@joe-job.com> wrote:
> 
> > I am seeing large latencies (600-2000 usec) latencies in
> > dcache_readdir.  This started when the machine became a Samba server
> > and the dcache presumably got large.  Traces are at the above url (8
> > and 9 I believe).  I think this patch fixes it.
> > 
> > --- fs/libfs.c~	2004-08-14 06:54:47.000000000 -0400
> > +++ fs/libfs.c	2004-08-27 00:44:17.000000000 -0400
> > @@ -140,6 +140,7 @@
> >  			}
> >  			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
> >  				struct dentry *next;
> > +				voluntary_resched_lock(&dcache_lock);
> >  				next = list_entry(p, struct dentry, d_child);
> >  				if (d_unhashed(next) || !next->d_inode)
> >  					continue;
> 
> In this loop we are iterating over the child-directories of this
> directory. In the next line (not shown in this patch) we drop the
> dcache_lock - so the issue is the 'continue' - where we skip already
> deleted entries. Are you positive this fixes the latencies you are
> seeing? The 'deleted entries' situation ought to be relatively rare.

No, I am not sure this fixes the problem.  This is a pretty rare one, I
only saw it twice.  I have not seen it since making the above change,
but this doesn't mean anything.

Lee