Eddie,

I implemented #2B and ran a three hour test with sles9-64 and rh4u4-64 guests. Each guest had 8 vcpus and the box was Intel with 2 physical processors. The guests were running large loads. Clock was pit. This is my usual test setup, except that I just as often used AMD nodes with more processors.

The time error was .02%, good enough for ntpd.

The implementation keeps a constant guest tsc offset. There is no pending_nr cancellation. When the vpt.c timer expires, it only increments pending_nr if its value is zero. Missed_ticks() is still calculated, but only to update the new timeout value. There is no adjustment to the tsc offset (set_guest_time()) at clock interrupt delivery time nor at re-scheduling time.

So, I like this method better than the pending_nr subtract. I'm going to work on this some more and, if all goes well, propose a new code submission soon. I'll put some kind of policy switch in too, which we can discuss and modify, but it will be along the lines of what we discussed below.

Thanks for your input!