you_bear zhou
2009-May-11 17:09 UTC
[Xen-users] One question about vcpu-wake up in credit scheduler
Hei guys, I''m now trying to do an attacking to credit scheduler ( Xen 3.2.0). As far as I know, the credit scheduler ticks the current runnable vcpu each 10ms, and a vcpu can wake up with BOOST priority if it was in UNDER state before waking up. What I''m trying to do is modifying the cpu_idle loop in linux kernel, let the idle process first spins for 9ms and then invokes halt(). I expect the vcpu be blocked right before the tick bound and wakes up right after that, so it can keep using CPU without paying credits. However, I found the vcpu seldom woke up. Then I look into the cpu_idle(), it checks if the cpu needs to reschedule, if so, then stops the idle loop. when I change the spin interval to 25ms, it did wake up frequently. So I think the interrupts should come from the scheduler. But why the vcpu didn''t wake up with 9ms spin interval?? Can anyone explain this to me ? Best, Tina _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users