Pandaboard ES and SD card

[John Hay]

On Tue, Mar 04, 2014 at 04:50:31PM -0700, Ian Lepore wrote:
> On Mon, 2014-03-03 at 17:12 +0100, Svatopluk Kraus wrote:
> > Hi,
> > 
> > I finally have found time to install FreeBSD 11.0-CURRENT on Pandaboard ES
> > on my table. It's been installed to SD card.  When I boot to multiuser,
> > it's very very slow. It looks that SD card write performance is very poor.
> > When I boot to singleuser, it's OK. However, when I make root filesystem
> > read-write by one command and immediately readonly by second one, the
> > second one takes a few minutes to finish.
...
> 
> The "mount -uw / ; mount -ur /" is a completely separate thing.  That
> takes about 30 seconds on every sdcard-based system I have.  I don't
> know why, but it's really annoying.  I don't think it's a driver thing,
> it happens with several different drivers.

It is svn 230553 to vfs_subr.c that causes it.

##############
When doing vflush(WRITECLOSE), clean vnode pages.

Unmounts do vfs_msync() before calling VFS_UNMOUNT(), but there is
still a race allowing a process to dirty pages after msync
finished. Remounts rw->ro just left dirty pages in system.

--- head/sys/kern/vfs_subr.c	2012/01/17 01:08:01	230249
+++ head/sys/kern/vfs_subr.c	2012/01/25 20:54:09	230553
@@ -2496,6 +2496,18 @@
 		 * vnodes open for writing.
 		 */
 		if (flags & WRITECLOSE) {
+			if (vp->v_object != NULL) {
+				VM_OBJECT_LOCK(vp->v_object);
+				vm_object_page_clean(vp->v_object, 0, 0, 0);
+				VM_OBJECT_UNLOCK(vp->v_object);
+			}
+			error = VOP_FSYNC(vp, MNT_WAIT, td);
+			if (error != 0) {
+				VOP_UNLOCK(vp, 0);
+				vdrop(vp);
+				MNT_VNODE_FOREACH_ABORT(mp, mvp);
+				return (error);
+			}
 			error = VOP_GETATTR(vp, &vattr, td->td_ucred);
 			VI_LOCK(vp);
 
##############

I'm running with the pfsense patch which basically put an if() around it,
with a sysctl that is not set.

https://redmine.pfsense.org/projects/pfsense-tools/repository/revisions/008742971cb44d8c0f81929504ab7330442c4ba4/entry/patches/RELENG_8_3/vfs_subr_mount_RO.diff

With 230553 only the AVILA watchdog will reset the box everytime you make
a config change. I'm sure there must be something wrong or very un-optimal
with that code because with a very slow flash interface I cannot see how
doing "mount -u -w /; vi /etc/rc.conf; mount -u -r /", can cause the last
mount to take half a minute or more.

John
-- 
John Hay -- jhay at meraka.csir.co.za / jhay at meraka.org.za