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>

9 files changed, 152 insertions, 0 deletions

diff --git a/arch_init.c b/arch_init.c
index 8cff9c608f..7fbfe91ad5 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -191,6 +191,16 @@ static struct {
     .cache = NULL,
 };
 
+
+int64_t xbzrle_cache_resize(int64_t new_size)
+{
+    if (XBZRLE.cache != NULL) {
+        return cache_resize(XBZRLE.cache, new_size / TARGET_PAGE_SIZE) *
+            TARGET_PAGE_SIZE;
+    }
+    return pow2floor(new_size);
+}
+
 static void save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
         int cont, int flag)
 {
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
diff --git a/hmp.c b/hmp.c
index 2a03b446a1..8abb4bddb3 100644
--- a/hmp.c
+++ b/hmp.c
@@ -194,6 +194,12 @@ void hmp_info_migrate_capabilities(Monitor *mon)
     qapi_free_MigrationCapabilityStatusList(caps);
 }
 
+void hmp_info_migrate_cache_size(Monitor *mon)
+{
+    monitor_printf(mon, "xbzrel cache size: %" PRId64 " kbytes\n",
+                   qmp_query_migrate_cache_size(NULL) >> 10);
+}
+
 void hmp_info_cpus(Monitor *mon)
 {
     CpuInfoList *cpu_list, *cpu;
@@ -764,6 +770,19 @@ void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict)
     qmp_migrate_set_downtime(value, NULL);
 }
 
+void hmp_migrate_set_cache_size(Monitor *mon, const QDict *qdict)
+{
+    int64_t value = qdict_get_int(qdict, "value");
+    Error *err = NULL;
+
+    qmp_migrate_set_cache_size(value, &err);
+    if (err) {
+        monitor_printf(mon, "%s\n", error_get_pretty(err));
+        error_free(err);
+        return;
+    }
+}
+
 void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict)
 {
     int64_t value = qdict_get_int(qdict, "value");
diff --git a/hmp.h b/hmp.h
index 3390a9242d..6d6e53bd6e 100644
--- a/hmp.h
+++ b/hmp.h
@@ -26,6 +26,7 @@ void hmp_info_chardev(Monitor *mon);
 void hmp_info_mice(Monitor *mon);
 void hmp_info_migrate(Monitor *mon);
 void hmp_info_migrate_capabilities(Monitor *mon);
+void hmp_info_migrate_cache_size(Monitor *mon);
 void hmp_info_cpus(Monitor *mon);
 void hmp_info_block(Monitor *mon);
 void hmp_info_blockstats(Monitor *mon);
@@ -53,6 +54,7 @@ void hmp_migrate_cancel(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_capability(Monitor *mon, const QDict *qdict);
+void hmp_migrate_set_cache_size(Monitor *mon, const QDict *qdict);
 void hmp_set_password(Monitor *mon, const QDict *qdict);
 void hmp_expire_password(Monitor *mon, const QDict *qdict);
 void hmp_eject(Monitor *mon, const QDict *qdict);
diff --git a/migration.c b/migration.c
index 5a5333c44b..a6c007215a 100644
--- a/migration.c
+++ b/migration.c
@@ -511,6 +511,25 @@ void qmp_migrate_cancel(Error **errp)
     migrate_fd_cancel(migrate_get_current());
 }
 
+void qmp_migrate_set_cache_size(int64_t value, Error **errp)
+{
+    MigrationState *s = migrate_get_current();
+
+    /* Check for truncation */
+    if (value != (size_t)value) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
+                  "exceeding address space");
+        return;
+    }
+
+    s->xbzrle_cache_size = xbzrle_cache_resize(value);
+}
+
+int64_t qmp_query_migrate_cache_size(Error **errp)
+{
+    return migrate_xbzrle_cache_size();
+}
+
 void qmp_migrate_set_speed(int64_t value, Error **errp)
 {
     MigrationState *s;
diff --git a/migration.h b/migration.h
index cdf6787cbd..337e2255a8 100644
--- a/migration.h
+++ b/migration.h
@@ -108,4 +108,6 @@ int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);
 int migrate_use_xbzrle(void);
 int64_t migrate_xbzrle_cache_size(void);
 
+int64_t xbzrle_cache_resize(int64_t new_size);
+
 #endif
diff --git a/monitor.c b/monitor.c
index 13b681ab48..5227cf15e3 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2662,6 +2662,13 @@ static mon_cmd_t info_cmds[] = {
         .mhandler.info = hmp_info_migrate_capabilities,
     },
     {
+        .name       = "migrate_cache_size",
+        .args_type  = "",
+        .params     = "",
+        .help       = "show current migration xbzrle cache size",
+        .mhandler.info = hmp_info_migrate_cache_size,
+    },
+    {
         .name       = "balloon",
         .args_type  = "",
         .params     = "",
diff --git a/qapi-schema.json b/qapi-schema.json
index e3847c870c..dd16dbd4c3 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1395,6 +1395,33 @@
 { 'command': 'migrate_set_speed', 'data': {'value': 'int'} }
 
 ##
+# @migrate-set-cache-size
+#
+# Set XBZRLE cache size
+#
+# @value: cache size in bytes
+#
+# The size will be rounded down to the nearest power of 2.
+# The cache size can be modified before and during ongoing migration
+#
+# Returns: nothing on success
+#
+# Since: 1.2
+##
+{ 'command': 'migrate-set-cache-size', 'data': {'value': 'int'} }
+
+##
+# @query-migrate-cache-size
+#
+# query XBZRLE cache size
+#
+# Returns: XBZRLE cache size in bytes
+#
+# Since: 1.2
+##
+{ 'command': 'query-migrate-cache-size', 'returns': 'int' }
+
+##
 # @ObjectPropertyInfo:
 #
 # @name: the name of the property
diff --git a/qmp-commands.hx b/qmp-commands.hx
index a14db90bbe..e42b4e3138 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -520,6 +520,50 @@ Example:
 <- { "return": {} }
 
 EQMP
+{
+        .name       = "migrate-set-cache-size",
+        .args_type  = "value:o",
+        .mhandler.cmd_new = qmp_marshal_input_migrate_set_cache_size,
+    },
+
+SQMP
+migrate-set-cache-size
+---------------------
+
+Set cache size to be used by XBZRLE migration, the cache size will be rounded
+down to the nearest power of 2
+
+Arguments:
+
+- "value": cache size in bytes (json-int)
+
+Example:
+
+-> { "execute": "migrate-set-cache-size", "arguments": { "value": 536870912 } }
+<- { "return": {} }
+
+EQMP
+    {
+        .name       = "query-migrate-cache-size",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_query_migrate_cache_size,
+    },
+
+SQMP
+query-migrate-cache-size
+---------------------
+
+Show cache size to be used by XBZRLE migration
+
+returns a json-object with the following information:
+- "size" : json-int
+
+Example:
+
+-> { "execute": "query-migrate-cache-size" }
+<- { "return": 67108864 }
+
+EQMP
 
     {
         .name       = "migrate_set_speed",