Re: [PATCH 1 of 4] Improve ring management for memory events

["Andres Lagar-Cavilla" <andres@lagarcavilla.org>]

Olaf,
> On Mon, Nov 14, Andres Lagar-Cavilla wrote:
>
> I will do a more complete review later, a few comments below.
>
>
>> +    free_requests = RING_FREE_REQUESTS(&med->front_ring);
>> +    if ( unlikely(free_requests < d->max_vcpus) )
>> +    {
>> +        /* This may happen during normal operation (hopefully not
>> often). */
>> +        gdprintk(XENLOG_INFO, "mem_event request slots for domain %d:
>> %d\n",
>> +                               d->domain_id, free_requests);
>
> What is the purpose of this printk? The ring can and does fillup quickly
> with paging.

Well, we can tone down printk's to be debug level. I don't think they're
unnecessary if they're made an optional debug tool.

Question: I have one vcpu, how do I fill up the ring quickly? (outside of
foreign mappings)

Andres
>
>
>> +    if ( mem_event_ring_free(d, med) == 0 )
>> +    {
>> +        /* This *may* happen, but only when foreign mappings generate
>> events. */
>> +        gdprintk(XENLOG_WARNING, "possible lost mem_event for domain
>> %d\n",
>> +                                 d->domain_id);
>
> This printk is not needed, callers have to try again.
>
> Olaf
>