On Thu, May 20, 2010 at 02:38:16PM +0930, Rusty Russell wrote: > On Thu, 20 May 2010 02:31:50 pm Rusty Russell wrote: > > On Wed, 19 May 2010 05:36:42 pm Avi Kivity wrote: > > > > Note that this is a exclusive->shared->exclusive bounce only, too. > > > > > > > > > > A bounce is a bounce. > > > > I tried to measure this to show that you were wrong, but I was only able > > to show that you're right. How annoying. Test code below. > > This time for sure! What do you see? On my laptop: [mst@tuck testring]$ ./rusty1 share 0 1 CPU 1: share cacheline: 2820410 usec CPU 0: share cacheline: 2823441 usec [mst@tuck testring]$ ./rusty1 unshare 0 1 CPU 0: unshare cacheline: 2783014 usec CPU 1: unshare cacheline: 2782951 usec [mst@tuck testring]$ ./rusty1 lockshare 0 1 CPU 1: lockshare cacheline: 1888495 usec CPU 0: lockshare cacheline: 1888544 usec [mst@tuck testring]$ ./rusty1 lockunshare 0 1 CPU 0: lockunshare cacheline: 1889854 usec CPU 1: lockunshare cacheline: 1889804 usec So locked version seems to be faster than unlocked, and share/unshare not to matter? same on a workstation: [root@qus19 ~]# ./rusty1 unshare 0 1 CPU 0: unshare cacheline: 6037002 usec CPU 1: unshare cacheline: 6036977 usec [root@qus19 ~]# ./rusty1 lockunshare 0 1 CPU 1: lockunshare cacheline: 5734362 usec CPU 0: lockunshare cacheline: 5734389 usec [root@qus19 ~]# ./rusty1 lockshare 0 1 CPU 1: lockshare cacheline: 5733537 usec CPU 0: lockshare cacheline: 5733564 usec using another pair of CPUs gives a more drastic results: [root@qus19 ~]# ./rusty1 lockshare 0 2 CPU 2: lockshare cacheline: 4226990 usec CPU 0: lockshare cacheline: 4227038 usec [root@qus19 ~]# ./rusty1 lockunshare 0 2 CPU 0: lockunshare cacheline: 4226707 usec CPU 2: lockunshare cacheline: 4226662 usec [root@qus19 ~]# ./rusty1 unshare 0 2 CPU 0: unshare cacheline: 14815048 usec CPU 2: unshare cacheline: 14815006 usec The share test seems to never finish on the workstation. I am debugging this. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
