Re: [Qemu-devel] [PATCH v3 3/8] multifd: Create new next_packet_size field

[Eric Blake]

On 3/7/19 6:28 AM, Juan Quintela wrote:
> "Dr. David Alan Gilbert" <address@hidden> wrote:
>> * Juan Quintela (address@hidden) wrote:
>>> We need to send this field when we add compression support.  As we are
>>> still on x- stage, we can do this kind of changes.
>>>
>>> Signed-off-by: Juan Quintela <address@hidden>
>>
>> OK, so that kind of makes sense - in that what you want to do is read
>> the whole compressed chunk in one go.
>>
>> Consider it might be a good idea to add some spare entries here;
>> say a uint64_t dummy[4] so that if you need any more fields in the
>> future it'll be easy to add them without breaking compatibility.
> 
> We have a version field, so ... we can handle it relatively gratiously,
> but I see your point.
> 
> How many?

What is the current struct size? Is there a nice power-of-2 or
cache-line-size multiple to round it out to?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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