Re: [PATCH v6 2/3] virtio_balloon: introduce migration primitivesto balloon pages

From: Rik van Riel
Date: Wed Aug 08 2012 - 21:39:42 EST


On 08/08/2012 06:53 PM, Rafael Aquini wrote:
Memory fragmentation introduced by ballooning might reduce significantly
the number of 2MB contiguous memory blocks that can be used within a guest,
thus imposing performance penalties associated with the reduced number of
transparent huge pages that could be used by the guest workload.

Besides making balloon pages movable at allocation time and introducing
the necessary primitives to perform balloon page migration/compaction,
this patch also introduces the following locking scheme to provide the
proper synchronization and protection for struct virtio_balloon elements
against concurrent accesses due to parallel operations introduced by
memory compaction / page migration.
- balloon_lock (mutex) : synchronizes the access demand to elements of
struct virtio_balloon and its queue operations;
- pages_lock (spinlock): special protection to balloon pages list against
concurrent list handling operations;

Signed-off-by: Rafael Aquini<aquini@xxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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