Hi,
On 3/20/19 7:37 PM, Volodymyr Babchuk wrote:
Julien Grall writes:
Anyway, you should explain how you decide the placement of each
hypercall_preempt_check(). For instance, if the lists are quite big,
then you may want add a preempt check in the loop.
I see your point there. Check in the loop would require additional
logic. Is there any best practices? E.g. how often I should check for
preemption? Every N iterations of loop, where N is...
It depends on how complex are each iteration of the loop. For instance,
in the p2m code, we check preemption every 512 mappings freed (see
relinquish_p2m_mapping).
The key point here is to document the choice even if you wrote it is
"random". This will help in the future if we need to revise preemption
choice.
I'd prefer to do proper fix, if it does not require a big amount of
work. Otherwise I'll add document the current state.
proper fix and preemption cannot be in the same sentence :). This is a
judgment call based on the complexity of the code.
In the example I gave above, we decided arbitrarily to preempt every 512
iterations. We didn't have any number but though 512 iterations was a
good number.
I don't expect you to find the best place right now. I am only asking to
document just we know the choice was "arbitrary".
Cheers,
--
Julien Grall
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