[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 0/2] make hypercall preemption checks consistent

>>> On 04.03.14 at 12:52, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 04/03/14 11:21, Jan Beulich wrote:
>> - never preempt on the first iteration (ensure forward progress)
>> - never preempt on the last iteration (pointless/wasteful)
>> - do cheap checks first
>> 1: common: make hypercall preemption checks consistent
>> 2: x86: make hypercall preemption checks consistent
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> All in all, this is a good improvement over what is currently present.
> However, given the overhead of creating continuations (particularly for
> 32bit HVM guests, which have been seen to unconditionally fail the
> preemption check by the time the compat layer has run), some of these
> operations would probably be better having more than a single guaranteed
> operation.

I agree, but I wanted to do one step at a time. Judging how much
work we want to permit done between preemption points will be
either heavy guess work, or require quite a bit of performance


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.