[Qemu-devel] [QEMU 3/7] Add the hmp and qmp interface for dropping cache

[Liang Li]

Add the hmp and qmp interface to drop vm's page cache, users
can control the type of cache they want vm to drop.

Signed-off-by: Liang Li <address@hidden>
---
 balloon.c        | 19 +++++++++++++++++++
 hmp-commands.hx  | 15 +++++++++++++++
 hmp.c            | 22 ++++++++++++++++++++++
 hmp.h            |  3 +++
 monitor.c        | 18 ++++++++++++++++++
 qapi-schema.json | 35 +++++++++++++++++++++++++++++++++++
 qmp-commands.hx  | 23 +++++++++++++++++++++++
 7 files changed, 135 insertions(+)

diff --git a/balloon.c b/balloon.c
index 0fb34bf..3d96111 100644
--- a/balloon.c
+++ b/balloon.c
@@ -122,3 +122,22 @@ void qmp_balloon(int64_t target, Error **errp)
     trace_balloon_event(balloon_opaque, target);
     balloon_event_fn(balloon_opaque, target);
 }
+
+void qmp_balloon_drop_cache(DropCacheType type, Error **errp)
+{
+    if (!have_balloon(errp)) {
+        return;
+    }
+
+    if (!balloon_drop_cache_fn) {
+        error_setg(errp, QERR_UNSUPPORTED);
+        return;
+    }
+    if (type < 0 && type >= DROP_CACHE_TYPE__MAX) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "type",
+                   "a value in range[0, 3]");
+        return;
+    }
+
+    balloon_drop_cache_fn(balloon_opaque, type);
+}
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 98b4b1a..c73572c 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1378,6 +1378,21 @@ Request VM to change its memory allocation to 
@var{value} (in MB).
 ETEXI
 
     {
+        .name       = "balloon_drop_cache",
+        .args_type  = "type:s",
+        .params     = "type",
+        .help       = "request VM to drop its page caches",
+        .mhandler.cmd = hmp_balloon_drop_cache,
+        .command_completion = balloon_drop_cache_completion
+    },
+
+STEXI
address@hidden balloon_drop_cache @var{type}
address@hidden balloon_drop_cache
+Request VM to dorp its page caches.
+ETEXI
+
+    {
         .name       = "set_link",
         .args_type  = "name:s,up:b",
         .params     = "name on|off",
diff --git a/hmp.c b/hmp.c
index a4b1d3d..3aa1062 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1061,6 +1061,28 @@ void hmp_balloon(Monitor *mon, const QDict *qdict)
     }
 }
 
+void hmp_balloon_drop_cache(Monitor *mon, const QDict *qdict)
+{
+    const char *type = qdict_get_str(qdict, "type");
+    Error *err = NULL;
+    int i;
+
+    for (i = 0; i < DROP_CACHE_TYPE__MAX; i++) {
+        if (strcmp(type, DropCacheType_lookup[i]) == 0) {
+            qmp_balloon_drop_cache(1 + i, &err);
+            break;
+        }
+    }
+
+    if (i == DROP_CACHE_TYPE__MAX) {
+        error_setg(&err, QERR_INVALID_PARAMETER, type);
+    }
+
+    if (err) {
+        error_report_err(err);
+    }
+}
+
 void hmp_block_resize(Monitor *mon, const QDict *qdict)
 {
     const char *device = qdict_get_str(qdict, "device");
diff --git a/hmp.h b/hmp.h
index 093d65f..6bb6499 100644
--- a/hmp.h
+++ b/hmp.h
@@ -55,6 +55,7 @@ void hmp_nmi(Monitor *mon, const QDict *qdict);
 void hmp_set_link(Monitor *mon, const QDict *qdict);
 void hmp_block_passwd(Monitor *mon, const QDict *qdict);
 void hmp_balloon(Monitor *mon, const QDict *qdict);
+void hmp_balloon_drop_cache(Monitor *mon, const QDict *qdict);
 void hmp_block_resize(Monitor *mon, const QDict *qdict);
 void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict);
 void hmp_snapshot_blkdev_internal(Monitor *mon, const QDict *qdict);
@@ -120,6 +121,8 @@ void watchdog_action_completion(ReadLineState *rs, int 
nb_args,
                                 const char *str);
 void migrate_set_capability_completion(ReadLineState *rs, int nb_args,
                                        const char *str);
+void balloon_drop_cache_completion(ReadLineState *rs, int nb_args,
+                                   const char *str);
 void migrate_set_parameter_completion(ReadLineState *rs, int nb_args,
                                       const char *str);
 void host_net_add_completion(ReadLineState *rs, int nb_args, const char *str);
diff --git a/monitor.c b/monitor.c
index a27e115..eefdf3d 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3367,6 +3367,24 @@ void migrate_set_parameter_completion(ReadLineState *rs, 
int nb_args,
     }
 }
 
+void balloon_drop_cache_completion(ReadLineState *rs, int nb_args,
+                                   const char *str)
+{
+    size_t len;
+
+    len = strlen(str);
+    readline_set_completion_index(rs, len);
+    if (nb_args == 2) {
+        int i;
+        for (i = 0; i < DROP_CACHE_TYPE__MAX; i++) {
+            const char *name = DropCacheType_lookup[i];
+            if (!strncmp(str, name, len)) {
+                readline_add_completion(rs, name);
+            }
+        }
+    }
+}
+
 void host_net_add_completion(ReadLineState *rs, int nb_args, const char *str)
 {
     int i;
diff --git a/qapi-schema.json b/qapi-schema.json
index 8483bdf..117f70a 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1655,6 +1655,41 @@
 { 'command': 'balloon', 'data': {'value': 'int'} }
 
 ##
+# @DropCacheType
+#
+# Cache types enumeration
+#
+# @clean: Drop the clean page cache.
+#
+# @slab: Drop the slab cache.
+#
+# @all: Drop both the clean and the slab cache.
+#
+# Since: 2.7
+##
+{ 'enum': 'DropCacheType', 'data': ['clean', 'slab', 'all'] }
+
+##
+# @balloon_drop_cache:
+#
+# Request the vm to drop its cache.
+#
+# @value: the type of cache want vm to drop
+#
+# Returns: Nothing on success
+#          If the balloon driver is enabled but not functional because the KVM
+#            kernel module cannot support it, KvmMissingCap
+#          If no balloon device is present, DeviceNotActive
+#
+# Notes: This command just issues a request to the guest.  When it returns,
+#        the drop cache operation may not have completed.  A guest can drop its
+#        cache independent of this command.
+#
+# Since: 2.7.0
+##
+{ 'command': 'balloon_drop_cache', 'data': {'value': 'DropCacheType'} }
+
+##
 # @Abort
 #
 # This action can be used to test transaction failure.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 28801a2..6650ba0 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1802,6 +1802,29 @@ Example:
 EQMP
 
     {
+        .name       = "balloon_drop_cache",
+        .args_type  = "value:i",
+        .mhandler.cmd_new = qmp_marshal_balloon_drop_cache,
+    },
+
+SQMP
+balloon_drop_cache
+-------
+
+Request VM to drop its cache.
+
+Arguments:
+
+- "value": cache type to drop (json-int)
+
+Example:
+
+-> { "execute": "balloon_drop_cache", "arguments": { "value": 1 } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "set_link",
         .args_type  = "name:s,up:b",
         .mhandler.cmd_new = qmp_marshal_set_link,
-- 
1.9.1