Yanfei Xu <yanfei...@bytedance.com> writes:
> There won't be any ram sync after the stage of save_complete, therefore
> it's unnecessary to do manually protect for dirty pages being sent. Skip
> to do this in last round can reduce noticeable downtime.
>
> Signed-off-by: Yanfei Xu <yanfei...@bytedance.com>
> ---
> As I don't have proper machine to test this patch in qemu and verify if it has
> risks like in postcopy, colo and so on.(But I tested this idea on my rust VMM,
> it works and can reduce ~50ms for a 128GB guest). So I raise the patch with
> RFC
> for suggestions.
>
> migration/ram.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index e12913b43e..2b169cdd18 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -838,7 +838,9 @@ static inline bool migration_bitmap_clear_dirty(RAMState
> *rs,
> * the page in the chunk we clear the remote dirty bitmap for all.
> * Clearing it earlier won't be a problem, but too late will.
> */
> - migration_clear_memory_region_dirty_bitmap(rb, page);
> + if (!rs->last_stage) {
> + migration_clear_memory_region_dirty_bitmap(rb, page);
> + }
>
> ret = test_and_clear_bit(page, rb->bmap);
> if (ret) {
Well, it looks ok to me and passes all my tests.
Tested-by: Fabiano Rosas <faro...@suse.de>
Reviewed-by: Fabiano Rosas <faro...@suse.de>
