Add migrate_set_cache_size command

Change XBZRLE cache size in bytes (the size should be a power of 2, it will be
rounded down to the nearest power of 2).
If XBZRLE cache size is too small there will be many cache miss.

New query-migrate-cache-size QMP command and 'info migrate_cache_size' HMP
command to query cache value.

Signed-off-by: Benoit Hudzia <benoit.hudzia@sap.com>
Signed-off-by: Petter Svard <petters@cs.umu.se>
Signed-off-by: Aidan Shribman <aidan.shribman@sap.com>
Signed-off-by: Orit Wasserman <owasserm@redhat.com>

Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 476b3cda2e..f6104b099f 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -829,6 +829,26 @@ STEXI
 @item migrate_cancel
 @findex migrate_cancel
 Cancel the current VM migration.
+
+ETEXI
+
+    {
+        .name       = "migrate_set_cache_size",
+        .args_type  = "value:o",
+        .params     = "value",
+        .help       = "set cache size (in bytes) for XBZRLE migrations,"
+                      "the cache size will be rounded down to the nearest "
+                      "power of 2.\n"
+                      "The cache size affects the number of cache misses."
+                      "In case of a high cache miss ratio you need to increase"
+                      " the cache size",
+        .mhandler.cmd = hmp_migrate_set_cache_size,
+    },
+
+STEXI
+@item migrate_set_cache_size @var{value}
+@findex migrate_set_cache_size
+Set cache size to @var{value} (in bytes) for xbzrle migrations.
 ETEXI
 
     {
@@ -1433,6 +1453,8 @@ show user network stack connection states
 show migration status
 @item info migrate_capabilities
 show current migration capabilities
+@item info migrate_cache_size
+show current migration XBZRLE cache size
 @item info balloon
 show balloon information
 @item info qtree