Re: [Qemu-devel] [PATCH] Add warmup phase for live migration of large memory apps

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/12/2011 06:23 AM, Shribman, Aidan wrote:
>> From: Juan Quintela [mailto:quintela@redhat.com]
>>
>>> If there are no additional dirty pages to be sent
>>> i.e. ram_save_remaining() == 0 then the migration *will* converge
>>> (even though we don't want it to) see:
>>
>> This should be a really idle guest to have that O:-)
>>
>> But if that is the whole problem, I would change the code to make the
>> case of max_downtime == 0 to mean that migration didn't converge.
>>
>
> I agree this would be fine as surrogate for the warmup patch as I proposed. New patch based on your's / Anthony's suggestion:
>
> ---
> diff --git a/arch_init.c b/arch_init.c
> index 4486925..9a35411 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -295,7 +295,8 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
>
>       expected_time = ram_save_remaining() * TARGET_PAGE_SIZE / bwidth;
>
> -    return (stage == 2)&&  (expected_time<= migrate_max_downtime());
> +    return (stage == 2)&&  migrate_max_downtime()&&
> +        (expected_time<= migrate_max_downtime());
>   }


This is better but let's make sure to document this behavior (and please 
include a Signed-off-by: in the next patch).

Regards,

Anthony Liguori

>   static inline void *host_from_stream_offset(QEMUFile *f,
> ---
>
> Best,
> Aidan