Date: Tue, 27 Jul 2010 09:35:52 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org, alc@freebsd.org Cc: Matthew Fleming <mdf356@gmail.com>, Andriy Gapon <avg@freebsd.org> Subject: Re: amd64: change VM_KMEM_SIZE_SCALE to 1? Message-ID: <201007270935.52082.jhb@freebsd.org> In-Reply-To: <AANLkTimWcXHAz=K1UM6ECa=6xR5KuS-sf_nDhbFEgehq@mail.gmail.com> References: <4C4DB2B8.9080404@freebsd.org> <4C4DD1AA.3050906@freebsd.org> <AANLkTimWcXHAz=K1UM6ECa=6xR5KuS-sf_nDhbFEgehq@mail.gmail.com>
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On Monday, July 26, 2010 3:30:59 pm Alan Cox wrote:
> As far as eliminating or reducing the manual tuning that many ZFS users do,
> I would love to see someone tackle the overly conservative hard limit that
> we place on the number of vnode structures. The current hard limit was put
> in place when we had just introduced mutexes into many structures and more a
> mutex was much larger than it is today.
I have a strawman of that (relative to 7). It simply adjusts the hardcoded
maximum to instead be a function of the amount of physical memory.
Index: vfs_subr.c
===================================================================
--- vfs_subr.c (revision 210934)
+++ vfs_subr.c (working copy)
@@ -288,6 +288,7 @@
static void
vntblinit(void *dummy __unused)
{
+ int vnodes;
/*
* Desiredvnodes is a function of the physical memory size and
@@ -299,10 +300,19 @@
desiredvnodes = min(maxproc + cnt.v_page_count / 4, 2 * vm_kmem_size /
(5 * (sizeof(struct vm_object) + sizeof(struct vnode))));
if (desiredvnodes > MAXVNODES_MAX) {
+
+ /*
+ * If there is a lot of physical memory, allow the cap
+ * on vnodes to expand to using a little under 1% of
+ * available RAM.
+ */
+ vnodes = max(MAXVNODES_MAX, cnt.v_page_count * (PAGE_SIZE /
+ 128) / (sizeof(struct vm_object) + sizeof(struct vnode)));
+ KASSERT(vnodes < desiredvnodes, ("capped vnodes too big"));
if (bootverbose)
printf("Reducing kern.maxvnodes %d -> %d\n",
- desiredvnodes, MAXVNODES_MAX);
- desiredvnodes = MAXVNODES_MAX;
+ desiredvnodes, vnodes);
+ desiredvnodes = vnodes;
}
wantfreevnodes = desiredvnodes / 4;
mtx_init(&mntid_mtx, "mntid", NULL, MTX_DEF);
--
John Baldwin
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