On 04/05/2013 07:46 AM, Anthony Liguori wrote: > The char-flow refactoring introduced a busy-wait that depended on > an action from the VCPU thread. However, the VCPU thread could > never take that action because the busy-wait starved the VCPU thread > of the BQL because it never dropped the mutex while running select. > > Paolo doesn't want to drop this optimization for fear that we will > stop detecting these busy waits. I'm afraid to keep this optimization > even with the busy-wait fixed because I think a similar problem can > occur just with heavy I/O thread load manifesting itself as VCPU pauses. > > As a compromise, introduce an artificial timeout after a thousand > iterations but print a rate limited warning when this happens. This > let's us still detect when this condition occurs without it being > a fatal error. >
> + * print a message to the screen. If we run into this condition, create > + * an fake timeout in order to give the VCPU threads a chance to run. s/an fake/a fake/ -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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