Re: [Qemu-devel] [PATCH] migratioin/ram: leave RAMBlock->bmap blank on allocating

[Wei Yang]

On Sat, Jun 01, 2019 at 11:34:41AM +0800, Peter Xu wrote:
>On Fri, May 31, 2019 at 05:43:37PM +0100, Dr. David Alan Gilbert wrote:
>> * Wei Yang (address@hidden) wrote:
>> > During migration, we would sync bitmap from ram_list.dirty_memory to
>> > RAMBlock.bmap in cpu_physical_memory_sync_dirty_bitmap().
>> > 
>> > Since we set RAMBlock.bmap and ram_list.dirty_memory both to all 1, this
>> > means at the first round this sync is meaningless and is a duplicated
>> > work.
>> > 
>> > Leaving RAMBlock->bmap blank on allocating would have a side effect on
>> > migration_dirty_pages, since it is calculated from the result of
>> > cpu_physical_memory_sync_dirty_bitmap(). To keep it right, we need to
>> > set migration_dirty_pages to 0 in ram_state_init().
>> > 
>> > Signed-off-by: Wei Yang <address@hidden>
>> 
>> I've looked at this for a while, and I think it's OK, so
>> 
>> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
>> 
>> Peter, Juan: Can you just see if there's arny reason this would be bad,
>> but I think it's actually more sensible than what we have.
>
>I really suspect it will work in all cases...  Wei, have you done any
>test (or better, thorough tests) with this change?  My reasoning of
>why we should need the bitmap all set is here:
>

I have done some migration cases, like migrate a linux guest through tcp.

Other cases suggested to do?

>https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg07361.html
>
>Regards,
>
>-- 
>Peter Xu

-- 
Wei Yang
Help you, Help me