On 29.07.21 22:00, Peter Xu wrote:
On Thu, Jul 29, 2021 at 09:39:24PM +0200, David Hildenbrand wrote:
In the meantime I adjusted the code but it does the clearing under the
iothread lock, which should not be what we want ... I'll have a look.
Thanks; if it takes more changes than expected we can still start from simple,
IMHO, by taking bql and timely yield it.
At the meantime, I found two things in ram_init_bitmaps() that I'm not sure we
need them of not:
1. Do we need WITH_RCU_READ_LOCK_GUARD() if with both bql and ramlist lock?
(small question)
Good question, I'm not sure if we need it.
2. Do we need migration_bitmap_sync_precopy() even if dirty bmap is all 1's?
(bigger question)
IIRC, the bitmap sync will fetch the proper dirty bitmap from KVM and set
the proper bits in the clear_bitmap. So once we call
migration_clear_memory_region_dirty_bitmap_range() etc. later we will
actually clear dirty bits.
Good point, however.. then I'm wondering whether we should just init clear_bmap
to all 1's too when init just like dirty bmap. :)
Yes, but ... I'm not sure if we have to get the dirty bits into
KVMSlot->dirty_bmap as well in order to clear them.
It could work with "manual_dirty_log_protect". For
!manual_dirty_log_protect we might have to keep it that way ... which
means we might have to expose some ugly details up to migration/ram.c .
Might require some thought :)
Besides: let's not be affected with these details as they should be more
suitable to be handled separately; maybe I'll follow this up. It could be a
place to discuss things, but shouldn't be a burden to block this series.
Agreed :)
--
Thanks,
David / dhildenb
