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migration: Use non-atomic ops for clear log bitmap

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Since we already have bitmap_mutex to protect either the dirty bitmap or
the clear log bitmap, we don't need atomic operations to set/clear/test on
the clear log bitmap.  Switching all ops from atomic to non-atomic
versions, meanwhile touch up the comments to show which lock is in charge.

Introduced non-atomic version of bitmap_test_and_clear_atomic(), mostly the
same as the atomic version but simplified a few places, e.g. dropped the
"old_bits" variable, and also the explicit memory barriers.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Xu 2022-10-04 14:24:29 -04:00 • committed by Juan Quintela
parent afed4273b5
commit cedb70eafb
4 changed files with 55 additions and 5 deletions
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3
include/exec/ramblock.h
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@ -53,6 +53,9 @@ struct RAMBlock {
* and split clearing of dirty bitmap on the remote node (e.g.,
* KVM). The bitmap will be set only when doing global sync.
*
* It is only used during src side of ram migration, and it is
* protected by the global ram_state.bitmap_mutex.
*
* NOTE: this bitmap is different comparing to the other bitmaps
* in that one bit can represent multiple guest pages (which is
* decided by the `clear_bmap_shift' variable below). On