PV i386 patch

[Sean Bruno]

On Thu, 2011-12-29 at 14:52 -0800, Alan Cox wrote:
> On 12/29/2011 16:28, Sean Bruno wrote:
> > On Thu, 2011-12-29 at 12:22 -0800, Alan Cox wrote:
> >> Please try this patch.  It eliminates a race condition that might
> >> actually account for some of the crashes in FreeBSD>= 9 on Xen.
> >>
> >> Alan
> >>
> > ref10-xen32.freebsd.org has this applied now.  Looks ok to me?
> >
> 
> 
> I know that lmbench's bw_pipe program exercises the code path that I 
> changed if you want to give it a bit more testing.
> 
> Alan
> 

Ok, I ran "a thing" ... I have a lot of poking around to do in lmbench
now.  Thanks for pointing me at this.

Cursory run with patch "xen-pmap.c"

[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe
Pipe bandwidth: 892.52 MB/sec
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe -N 5
Pipe bandwidth: 982.46 MB/sec
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe -N 5 -P 2
Pipe bandwidth: 899.34 MB/sec

Cursory run of vanilla-current:
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe
Pipe bandwidth: 984.37 MB/sec
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe -N 5
Pipe bandwidth: 977.54 MB/sec
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ ./bw_pipe -N 5 -P 2
Pipe bandwidth: 887.26 MB/sec
[sbruno at ref10-xen32 /usr/local/lib/lmbench/bin/i386-freebsd10.0]$ uname
-a
FreeBSD ref10-xen32.freebsd.org 10.0-CURRENT FreeBSD 10.0-CURRENT #1
r228971: Fri Dec 30 18:27:01 UTC 2011
sbruno at ref10-xen32.freebsd.org:/var/tmp/dumpster/scratch/sbruno-scratch/head/sys/XEN  i386