Re: [Qemu-devel] [PATCH 16/17] migration: adjust migration_thread() process for page flipping

[Lei Li <lilei@linux.vnet.ibm.com>]

On 11/26/2013 07:32 PM, Paolo Bonzini wrote:
> Il 21/11/2013 10:11, Lei Li ha scritto:
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>   migration.c |   10 +++++++---
>>   1 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/migration.c b/migration.c
>> index 4ac466b..0f98ac1 100644
>> --- a/migration.c
>> +++ b/migration.c
>> @@ -579,10 +579,11 @@ static void *migration_thread(void *opaque)
>>               pending_size = qemu_savevm_state_pending(s->file, max_size);
>>               DPRINTF("pending size %" PRIu64 " max %" PRIu64 "\n",
>>                       pending_size, max_size);
>> -            if (pending_size && pending_size >= max_size) {
>> +            if (pending_size && pending_size >= max_size &&
>> +                !runstate_needs_reset()) {
>>                   qemu_savevm_state_iterate(s->file);
> I'm not sure why you need this.

The adjustment here is to avoid the iteration stage for page flipping.
Because pending_size = ram_save_remaining() * TARGET_PAGE_SIZE which is
not 0 and pending_size > max_size (0) at start.

In the previous version it was like this:

if (pending_size && pending_size >= max_size &&
     !migrate_unix_page_flipping()) {

And you said 'This is a bit ugly but I understand the need. Perhaps "&&
!runstate_needs_reset()" like below?' :)

>
>>               } else {
>> -                int ret;
>> +                int ret = 0;
>>   
>>                   DPRINTF("done iterating\n");
>>                   qemu_mutex_lock_iothread();
>> @@ -590,7 +591,10 @@ static void *migration_thread(void *opaque)
>>                   qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
>>                   old_vm_running = runstate_is_running();
>>   
>> -                ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
>> +                if (!runstate_needs_reset()) {
>> +                    ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
>> +                }
> This however is okay.
>
> Paolo
>
>>                   if (ret >= 0) {
>>                       qemu_file_set_rate_limit(s->file, INT_MAX);
>>                       qemu_savevm_state_complete(s->file);
>>
>


-- 
Lei