[Qemu-devel] [RFC 3/3] memory/qmp: add set-memory-merge command

[Luiz Capitulino]

Allow to enable/disable memory merging during run-time.

This is implemented by extending the qemu_set_mem_merge() function.

To test on HMP:

  (qemu) set_memory_merge on
  (qemu) set_memory_merge off

Signed-off-by: Luiz Capitulino <address@hidden>
---
 exec.c           | 15 +++++++++++++++
 hmp-commands.hx  | 14 ++++++++++++++
 hmp.c            |  6 ++++++
 hmp.h            |  1 +
 monitor.c        |  6 ++++++
 osdep.h          |  2 ++
 qapi-schema.json | 18 ++++++++++++++++++
 qmp-commands.hx  |  5 +++++
 8 files changed, 67 insertions(+)

diff --git a/exec.c b/exec.c
index e29b27f..1fa82b4 100644
--- a/exec.c
+++ b/exec.c
@@ -2504,6 +2504,21 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char 
*name, DeviceState *dev)
 
 void qemu_set_mem_merge(bool value)
 {
+    const RAMBlock *block;
+
+    if (ram_list.merge_memory == value) {
+        /* do nothing */
+        return;
+    }
+
+    /* XXX: report errors? */
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        if (block->flags & RAM_MERGEABLE) {
+            qemu_madvise(block->host, block->length,
+                         value ? QEMU_MADV_MERGEABLE : QEMU_MADV_UNMERGEABLE);
+        }
+    }
+
     ram_list.merge_memory = value;
 }
 
diff --git a/hmp-commands.hx b/hmp-commands.hx
index f5d9d91..6ab3852 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -366,6 +366,20 @@ Wakeup guest from suspend.
 ETEXI
 
     {
+        .name       = "set_memory_merge",
+        .args_type  = "status:b",
+        .params     = "status",
+        .help       = "enable/disable memory merge support",
+        .mhandler.cmd = hmp_set_memory_merge,
+    },
+
+STEXI
address@hidden set_memory_merge
address@hidden set_memory_merge
+Enable/disable memory merge support
+ETEXI
+
+    {
         .name       = "gdbserver",
         .args_type  = "device:s?",
         .params     = "[device]",
diff --git a/hmp.c b/hmp.c
index b9cec1d..063cb3e 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1000,3 +1000,9 @@ void hmp_netdev_del(Monitor *mon, const QDict *qdict)
     qmp_netdev_del(id, &err);
     hmp_handle_error(mon, &err);
 }
+
+void hmp_set_memory_merge(Monitor *mon, const QDict *qdict)
+{
+    bool enable = qdict_get_bool(qdict, "status");
+    qmp_set_memory_merge(enable, NULL);
+}
diff --git a/hmp.h b/hmp.h
index 79d138d..d884733 100644
--- a/hmp.h
+++ b/hmp.h
@@ -64,5 +64,6 @@ void hmp_device_del(Monitor *mon, const QDict *qdict);
 void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
 void hmp_netdev_add(Monitor *mon, const QDict *qdict);
 void hmp_netdev_del(Monitor *mon, const QDict *qdict);
+void hmp_set_memory_merge(Monitor *mon, const QDict *qdict);
 
 #endif
diff --git a/monitor.c b/monitor.c
index f6107ba..c7f9015 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4813,3 +4813,9 @@ int monitor_read_block_device_key(Monitor *mon, const 
char *device,
 
     return monitor_read_bdrv_key_start(mon, bs, completion_cb, opaque);
 }
+
+/* FIXME: move to qmp.c, although including memory.h doesn't work there */
+void qmp_set_memory_merge(bool enable, Error **errp)
+{
+    memory_global_set_merge(enable);
+}
diff --git a/osdep.h b/osdep.h
index 3ea4af0..f5563c2 100644
--- a/osdep.h
+++ b/osdep.h
@@ -97,8 +97,10 @@ void qemu_vfree(void *ptr);
 #endif
 #ifdef MADV_MERGEABLE
 #define QEMU_MADV_MERGEABLE MADV_MERGEABLE
+#define QEMU_MADV_UNMERGEABLE MADV_UNMERGEABLE
 #else
 #define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
+#define QEMU_MADV_UNMERGEABLE QEMU_MADV_INVALID
 #endif
 
 #elif defined(CONFIG_POSIX_MADVISE)
diff --git a/qapi-schema.json b/qapi-schema.json
index 3b6e346..0b99bc0 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1862,3 +1862,21 @@
 # Since: 0.14.0
 ##
 { 'command': 'netdev_del', 'data': {'id': 'str'} }
+
+##
+# @set-memory-merge:
+#
+# Enable or disable memory merge support. On Linux systems, this enables
+# or disables KSM support.
+#
+# @enable: true (enables memory merging) or false (disables memory merging)
+#
+# Returns: Nothing on success
+#
+# Note: this command never fails. The only possible reason for a failure
+# is when the host doesn't support memory merging, but that's not reported
+# by this command, it will just return success.
+#
+# Since: 1.2.0
+##
+{ 'command': 'set-memory-merge', 'data': { 'enable': 'bool' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 2e1a38e..74530b9 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2209,3 +2209,8 @@ EQMP
         .args_type  = "implements:s?,abstract:b?",
         .mhandler.cmd_new = qmp_marshal_input_qom_list_types,
     },
+    {
+        .name       = "set-memory-merge",
+        .args_type  = "enable:b",
+        .mhandler.cmd_new = qmp_marshal_input_set_memory_merge,
+    },
-- 
1.7.10.2.565.gbd578b5