Patchwork [v8,09/10] Add set_cachesize command

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Submitter Orit Wasserman
Date April 5, 2012, 10:47 a.m.
Message ID <1333622879-12055-10-git-send-email-owasserm@redhat.com>
Download mbox | patch
Permalink /patch/151172/
State New
Headers show

Comments

Orit Wasserman - April 5, 2012, 10:47 a.m.
Change XBZRLE cache size in MB (the size should be a power of 2).

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
---
 arch_init.c      |    8 ++++++++
 hmp-commands.hx  |   15 +++++++++++++++
 hmp.c            |   13 +++++++++++++
 hmp.h            |    1 +
 migration.c      |   31 ++++++++++++++++++++++++++++++-
 migration.h      |    2 ++
 qapi-schema.json |   13 +++++++++++++
 qmp-commands.hx  |   22 ++++++++++++++++++++++
 8 files changed, 104 insertions(+), 1 deletions(-)
Avi Kivity - April 5, 2012, 12:15 p.m.
On 04/05/2012 01:47 PM, Orit Wasserman wrote:
> Change XBZRLE cache size in MB (the size should be a power of 2).

In bytes

>  
> +void xbzrle_cache_resize(int64_t new_size)
> +{
> +    if (page_cache) {
> +        cache_fini();
> +        cache_init(new_size);
> +    }
> +}

A little sad to drop the cache, especially if we're enlarging it.  But
this can be improved later.

> +
> +ETEXI
> +
> +    {
> +        .name       = "migrate_set_cachesize",
> +        .args_type  = "value:o",
> +        .params     = "value",
> +        .help       = "set cache size (in MB) for XBZRLE migrations",

In bytes.

> +        .mhandler.cmd = hmp_migrate_set_cachesize,
> +    },
> +
> +STEXI
> +@item migrate_set_cachesize @var{value}
> +@findex migrate_set_cache
> +Set cache size to @var{value} (in MB) for xbzrle migrations.

Need to document the constraints, and say something about how a larger
cache size can reduce the needed bandwidth.

We need to either document the default or (better) add a command to get
the current cache size (perhaps with some statistics about hit rate and
average data reduction).

>  
> +void qmp_migrate_set_cachesize(int64_t value, Error **errp)
> +{
> +    MigrationState *s;
> +
> +    /* On 32-bit hosts, QEMU is limited by virtual address space */
> +    if (value > (2047 << 20) && HOST_LONG_BITS == 32) {

Could be made clearer by using

   /* Check for truncation */
   if (value != (size_t)value)) {
      ...

(assumes value is in bytes)

>  ##
> +# @migrate_set_cachesize
> +#
> +# Set XBZRLE cache size
> +#
> +# @value: cache size in bytes

Here it's in bytes, good.

For the human monitor we can use MB as the unit, or allow suffixes as we
do for -m <memory>.

Patch

diff --git a/arch_init.c b/arch_init.c
index d728e5a..9df9d1c 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -174,6 +174,14 @@  typedef struct __attribute__((packed)) XBZRLEHeader {
 
 static uint8 *prev_cache_page;
 
+void xbzrle_cache_resize(int64_t new_size)
+{
+    if (page_cache) {
+        cache_fini();
+        cache_init(new_size);
+    }
+}
+
 /***********************************************************/
 /* XBRLE page cache implementation */
 static CacheItem *cache_item_get(unsigned long pos, int item)
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 88e345a..31a5eb7 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -834,6 +834,21 @@  STEXI
 @item migrate_cancel
 @findex migrate_cancel
 Cancel the current VM migration.
+
+ETEXI
+
+    {
+        .name       = "migrate_set_cachesize",
+        .args_type  = "value:o",
+        .params     = "value",
+        .help       = "set cache size (in MB) for XBZRLE migrations",
+        .mhandler.cmd = hmp_migrate_set_cachesize,
+    },
+
+STEXI
+@item migrate_set_cachesize @var{value}
+@findex migrate_set_cache
+Set cache size to @var{value} (in MB) for xbzrle migrations.
 ETEXI
 
     {
diff --git a/hmp.c b/hmp.c
index 186a119..c1b5380 100644
--- a/hmp.c
+++ b/hmp.c
@@ -740,6 +740,19 @@  void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict)
     qmp_migrate_set_downtime(value, NULL);
 }
 
+void hmp_migrate_set_cachesize(Monitor *mon, const QDict *qdict)
+{
+    int64_t value = qdict_get_int(qdict, "value");
+    Error *err = NULL;
+
+    qmp_migrate_set_cachesize(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 1c53d35..02a10ee 100644
--- a/hmp.h
+++ b/hmp.h
@@ -52,6 +52,7 @@  void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict);
 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_cachesize(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 db8c3d8..ec51ad3 100644
--- a/migration.c
+++ b/migration.c
@@ -166,7 +166,7 @@  MigrationCapList *qmp_query_migration_caps(Error **errp)
     MigrationCapList *caps_list = g_malloc0(sizeof(*caps_list));
 
     caps_list->value = g_malloc(sizeof(*caps_list->value));
-    caps_list->value->name = g_strdup("uleb");
+    caps_list->value->name = g_strdup("xbzrle");
     caps_list->next = NULL;
 
     return caps_list;
@@ -464,6 +464,35 @@  void qmp_migrate_cancel(Error **errp)
     migrate_fd_cancel(migrate_get_current());
 }
 
+void qmp_migrate_set_cachesize(int64_t value, Error **errp)
+{
+    MigrationState *s;
+
+    /* On 32-bit hosts, QEMU is limited by virtual address space */
+    if (value > (2047 << 20) && HOST_LONG_BITS == 32) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
+                  "exceeding address space");
+        return;
+    }
+
+    /* power of 2 */
+    if (value != 1 && (value & (value - 1))) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
+                  "needs to be power of 2");
+        return;
+    }
+
+    value = MIN(UINT64_MAX, value);
+    if (value ==  migrate_cache_size) {
+        return;
+    }
+
+    migrate_cache_size =  value;
+    s = migrate_get_current();
+    s->params.xbzrle_cache_size = value;
+    xbzrle_cache_resize(value);
+}
+
 void qmp_migrate_set_speed(int64_t value, Error **errp)
 {
     MigrationState *s;
diff --git a/migration.h b/migration.h
index 06ce8ab..3426c94 100644
--- a/migration.h
+++ b/migration.h
@@ -109,4 +109,6 @@  int decode_page(uint8_t *src, int slen, uint8_t *dst, int dlen);
 int migrate_use_xbzrle(void);
 int64_t migrate_xbzrle_cache_size(void);
 
+void xbzrle_cache_resize(int64_t new_size);
+
 #endif
diff --git a/qapi-schema.json b/qapi-schema.json
index e49ec43..f055ec6 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1310,6 +1310,19 @@ 
 { 'command': 'migrate_set_speed', 'data': {'value': 'int'} }
 
 ##
+# @migrate_set_cachesize
+#
+# Set XBZRLE cache size
+#
+# @value: cache size in bytes
+#
+# Returns: nothing on success
+#
+# Since: 1.1
+##
+{ 'command': 'migrate_set_cachesize', 'data': {'value': 'int'} }
+
+##
 # @ObjectPropertyInfo:
 #
 # @name: the name of the property
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c21ec1c..5aa26ba 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -525,6 +525,28 @@  Example:
 <- { "return": {} }
 
 EQMP
+{
+        .name       = "migrate_set_cachesize",
+        .args_type  = "value:o",
+        .mhandler.cmd_new = qmp_marshal_input_migrate_set_cachesize,
+    },
+
+SQMP
+migrate_set_cachesize
+---------------------
+
+Set cache size to be used by XBZRLE migration
+
+Arguments:
+
+- "value": cache size in bytes (json-int)
+
+Example:
+
+-> { "execute": "migrate_set_cachesize", "arguments": { "value": 512 } }
+<- { "return": {} }
+
+EQMP
 
     {
         .name       = "migrate_set_speed",