Date: Tue, 6 May 1997 13:01:45 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Poul-Henning Kamp <phk@dk.tfs.com> Cc: current@freebsd.org Subject: Re: vnode->v_usage Message-ID: <Pine.BSF.3.95q.970506125821.331J-100000@herring.nlsystems.com> In-Reply-To: <207.862417862@critter>
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On Wed, 30 Apr 1997, Poul-Henning Kamp wrote:
> In message <Pine.BSF.3.95q.970427143216.346G-100000@herring.nlsystems.com>, Dou
> g Rabson writes:
> >On Sun, 27 Apr 1997, Poul-Henning Kamp wrote:
> >>
> >> Unless somebody convinces me of the utility of this field, I will remove
> >> it from the vnodes.
> >>
> >I think it is intended to be used to keep frequently used vnodes from
> >being recycled by getnewvnode.
>
> Well, I've done it. Here is a patch that implements LRU for name-cache
> hits on the vnode freelist. I doubt that it has any performance impact,
> but it makes the vnode 4 bytes smaller, which is a good thing.
>
> Please test and report.
>
> Recompile or rename your LKMs before trying this!
I just had a page fault in vtouch. The code needs to check for
v_freelist.tqe_prev != 0xdeadb (shudder) to protect itself from races with
getnewvnode.
Index: vfs_subr.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/vfs_subr.c,v
retrieving revision 1.85
diff -u -r1.85 vfs_subr.c
--- vfs_subr.c 1997/05/04 09:17:29 1.85
+++ vfs_subr.c 1997/05/06 11:57:05
@@ -2149,8 +2149,10 @@
return;
}
if (simple_lock_try(&vnode_free_list_slock)) {
- TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
- TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
+ if (vp->v_freelist.tqe_prev != (struct vnode **)0xdeadb) {
+ TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
+ TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
+ }
simple_unlock(&vnode_free_list_slock);
}
simple_unlock(&vp->v_interlock);
--
Doug Rabson Mail: dfr@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 951 1891
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