Hi Atsuhi. On Mon, Aug 21, 2006 at 08:38:33PM +0900, Atsushi SAKAI wrote:
> 2)The VIRQ_ITC cycle is destroyed > in case vcpu migration occurred when vcpu_pend_timer runs (called by > hlt_timer_fn) > > The VIRQ_ITC cycle is (simple writing) > ia64_get_itc reaches domain_itm at Xen. > send VIRQ_ITC to GuestOS > GuestOS handles and set next itm by hypercall to Xen > Repeats. > > > Currently, the function order in vcpu_pend_timer is > a)send VIRQ_ITC(vcpu_pend_timer) > b)then stamp the signal send information.(update domain_itm_last) > In this configuration, > domain_itm_last update time and hypercall set itm(which comes from VIRQ_ITC) > is important. > > This order is problematic in case vcpu_migration occurred as follows > (following event occures nearly 1-2 hour running > by 2xDomU 3vcpu(total 6vcpu for domU) in 4pcpu Linux Kernel Compile test) > > [EMAIL PROTECTED] is started.(GuestOS is not running at this moment) > [EMAIL PROTECTED] > [EMAIL PROTECTED] is paused > Credit Scheduler steal vcpu from A to B > [EMAIL PROTECTED] is started and ended > > ******The following process should be after vcpu_pend_timer***** > domain_itm is set by GuestOS hypercall. and domain_itm updated. > > [EMAIL PROTECTED] is resumed. but domain_itm is already updated. > > > To avoid this, order should be exchanged b) a) > After this fixation, we are free from timing consideration of > VIRQ_ITC cycle and domain_itm_last update time. > (domain_itm_last update should be before the hypercall set itm) Could you elaborate more? I don't understand. What phenomenan did you observed? vcpu_pend_timer() is called with its parameter as current. It means that test_bit(_VCPUF_running, vcpu->vcpu_flags) is always true becuase vcpu == current. On the other hand, scheduler mustn't steal vcpu with _VCPUF_running set. (see __csched_vcpu_is_stealable()) The vcpu stealing doesn't occur so that the above sequence doesn't make sense (to me at least.) Thanks. -- yamahata _______________________________________________ Xen-ia64-devel mailing list Xen-ia64-devel@lists.xensource.com http://lists.xensource.com/xen-ia64-devel
