Re: [PATCH Remus v5 1/2] libxc/save: implement Remus checkpointed save

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 15/05/2015 03:12, Yang Hongyang wrote:
>
>>> @@ -467,6 +477,14 @@ static int send_domain_memory_live(struct
>>> xc_sr_context *ctx)
>>>       DECLARE_HYPERCALL_BUFFER_SHADOW(unsigned long, dirty_bitmap,
>>>                                       &ctx->save.dirty_bitmap_hbuf);
>>>
>>> +    /*
>>> +     * With Remus, we will enter checkpointed save after live
>>> migration.
>>> +     * In checkpointed save loop, we skip the live part and pause
>>> straight
>>> +     * away to send dirty pages between checkpoints.
>>> +     */
>>> +    if ( !ctx->save.live )
>>> +        goto last_iter;
>>
>> Rather than use goto would it work to refactor everything from here to
>> the label into some sort of helper and just call that in the "actually
>> live" case?
>>
>> Or perhaps everything from the label to the end should be a helper
>> function which the caller can also use in thecheckpoint case instead of
>> calling send_domain_memory_live (and which s_d_m_l also calls of
>> course).
>
> I'm going to refactor the send_domain_memory_live() as follows:
>
> split the send_domain_memory_live() into three helper function:
>   - send_memory_live()  do the actually live case
>   - suspend_and_send_dirty() suspend the guest and send dirty pages
>   - send_memory_verify()
>
> then:
>   - send_domain_memory_live() combination of those three helper functions
>   - send_domain_momory_checkpointed() calls suspend_and_send_dirty() and
>                                       send_memory_verify()
>   - send_domain_memory_nonlive() stay as it is
> Does it make sense?

verify mode is only a debugging tool, and shouldn't be used in general. 
(It is actually a lot less useful in retrospect than one would imagine.)

However, the rest of the split looks plausible.

~Andrew