On Wed, 2024-01-17 at 15:58 +0800, pet...@redhat.com wrote:
> From: Peter Xu <pet...@redhat.com>
>
> When the migration frameworks fetches the exact pending sizes, it means
> this check:
>
> remaining_size < s->threshold_size
>
> Must have been done already, actually at migration_iteration_run():
>
> if (must_precopy <= s->threshold_size) {
> qemu_savevm_state_pending_exact(&must_precopy, &can_postcopy);
>
> That should be after one round of ram_state_pending_estimate(). It makes
> the 2nd check meaningless and can be dropped.
>
> To say it in another way, when reaching ->state_pending_exact(), we
> unconditionally sync dirty bits for precopy.
>
> Then we can drop migrate_get_current() there too.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
Hi Peter,
could you have a look at this issue:
https://gitlab.com/qemu-project/qemu/-/issues/1565
which I reopened. Previous thread here:
https://lore.kernel.org/qemu-devel/20230324184129.3119575-1-...@linux.ibm.com/
I'm seeing migration failures with s390x TCG again, which look the same to me
as those a while back.
> ---
> migration/ram.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index c0cdcccb75..d5b7cd5ac2 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3213,21 +3213,20 @@ static void ram_state_pending_estimate(void *opaque,
> uint64_t *must_precopy,
> static void ram_state_pending_exact(void *opaque, uint64_t *must_precopy,
> uint64_t *can_postcopy)
> {
> - MigrationState *s = migrate_get_current();
> RAMState **temp = opaque;
> RAMState *rs = *temp;
> + uint64_t remaining_size;
>
> - uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
> -
> - if (!migration_in_postcopy() && remaining_size < s->threshold_size) {
> + if (!migration_in_postcopy()) {
> bql_lock();
> WITH_RCU_READ_LOCK_GUARD() {
> migration_bitmap_sync_precopy(rs, false);
> }
> bql_unlock();
> - remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
> }
>
> + remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
> +
> if (migrate_postcopy_ram()) {
> /* We can do postcopy, and all the data is postcopiable */
> *can_postcopy += remaining_size;
This basically reverts 28ef5339c3 ("migration: fix ram_state_pending_exact()"),
which originally
made the issue disappear.
Any thoughts on the matter appreciated.
Thanks,
Nina
