* Avi Kivity <avi@xxxxxxxxxx> [2010-08-02 03:33]: > On 07/26/2010 08:19 PM, Jeremy Fitzhardinge wrote: > > On 07/25/2010 11:14 PM, Srivatsa Vaddagiri wrote: > >>Add KVM hypercall for yielding vcpu timeslice. > > > >Can you do a directed yield? > > > > A problem with directed yield is figuring out who to yield to. One idea > is to look for a random vcpu that is not running and donate some runtime > to it. In the best case, it's the lock holder and we cause it to start > running. Middle case it's not the lock holder, but we lose enough > runtime to stop running, so at least we don't waste cpu. Worst case we > continue running not having woken the lock holder. Spin again, yield > again hoping to find the right vcpu. It's been quite some time, but played with directed yielding for Xen[1] and we were looking to model the POWER directed yield (H_CONFER) where the lock holding vcpu was indiciated in the spinlock. When acquiring the lock, record the vcpu id. When another vcpu attempts to acquire the lock if it can't it can yield its time to the lock holder. 1. http://lists.xensource.com/archives/html/xen-devel/2005-05/msg00776.html -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
