qcow2: mark the memory as no longer needed after qcow2_cache_empty()
After having emptied the cache, the data in the cache tables is no
longer useful, so we can tell the kernel that we are done with it. In
Linux this frees the resources associated with it.
The effect of this can be seen in the HMP commit operation: it moves
data from the top to the base image (and fills both caches), then it
empties the top image. At this point the data in that cache is no
longer needed so it's just wasting memory.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id:
08538b098e1faf6c92496477cf9b47a20e5aacea.
1438690126.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>