Re: [Xen-devel] RFC: mem_event: use wait queue when ring is full

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 23/11/2011 16:49, "Olaf Hering" <olaf@xxxxxxxxx> wrote:

> On Tue, Nov 22, Andres Lagar-Cavilla wrote:
> 
>> Olaf, two questions here
>> 
>> - do you have any insight for events caused by foreign mappings? Those
>> will be lost with a full ring, with or without wait queues
> 
> The callers of mem_event_check_ring() have to retry if the ring is full.
> Thats what happens with p2m_mem_paging_populate(), the callers return
> -ENOENT and expect a retry at some later point.
> 
>> - we have posted a patch (twice) previously, with changes to ring
>> management, most importantly sending guest vcpus to sleep when space in
>> the ring is < d->max_vcpus. I see these two patches as complementary. What
>> is your take?
> 
> I'm not proposing to include my patch as is, because it has one issue:
> wake_up will start all waiting vcpus even if there is just a single slot
> free in the ringbuffer. You patch is better in this respect because only
> a few will be started again.

Do you need a wake_up_one() function?

 -- Keir

> I will send comments for it later.
> 
> Olaf
> 
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