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

[Ingo Molnar <mingo@elte.hu>]

* 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.

	Ingo