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Re: [Qemu-devel] [RFC PATCH v1: 11/12] mc: register MC qemu-file functio


From: Michael R. Hines
Subject: Re: [Qemu-devel] [RFC PATCH v1: 11/12] mc: register MC qemu-file functions and expose MC tunable capability
Date: Wed, 06 Nov 2013 11:34:25 -0500
User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130329 Thunderbird/17.0.5

On 10/23/2013 07:00 AM, Isaku Yamahata wrote:
Since more integer parameters would come in the future, so how about
set_migrate_parameter similar to set_migrate_capability?
It sets integer value, while set_migrate_capability sets bool value.

thanks,

On Mon, Oct 21, 2013 at 01:14:21AM +0000,
address@hidden wrote:

From: "Michael R. Hines" <address@hidden>

The capability allows management software to throttle the MC frequency
during VM application transience.

The qemu-file savevm() functions inform the destination that the incoming
traffic is MC-specific traffic and not vanilla live-migration traffic.

Signed-off-by: Michael R. Hines <address@hidden>
---
  hmp-commands.hx  | 14 ++++++++++++++
  hmp.c            |  6 ++++++
  hmp.h            |  1 +
  qapi-schema.json | 13 +++++++++++++
  qmp-commands.hx  | 23 +++++++++++++++++++++++
  vl.c             |  3 +++
  6 files changed, 60 insertions(+)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index caae5ad..7db0597 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -960,6 +960,20 @@ Set maximum tolerated downtime (in seconds) for migration.
  ETEXI
{
+        .name       = "migrate-set-mc-delay",
+        .args_type  = "value:i",
+        .params     = "value",
+        .help       = "set maximum delay (in milliseconds) between 
micro-checkpoints",
+        .mhandler.cmd = hmp_migrate_set_mc_delay,
+    },
+
+STEXI
address@hidden migrate_set_downtime @var{second}
address@hidden migrate_set_downtime
+Set maximum tolerated downtime (in seconds) for migration.
+ETEXI
+
+    {
          .name       = "migrate_set_capability",
          .args_type  = "capability:s,state:b",
          .params     = "capability state",
diff --git a/hmp.c b/hmp.c
index 43896e9..8e89ac7 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1026,6 +1026,12 @@ void hmp_migrate_set_downtime(Monitor *mon, const QDict 
*qdict)
      qmp_migrate_set_downtime(value, NULL);
  }
+void hmp_migrate_set_mc_delay(Monitor *mon, const QDict *qdict)
+{
+    int64_t value = qdict_get_int(qdict, "value");
+    qmp_migrate_set_mc_delay(value, NULL);
+}
+
  void hmp_migrate_set_cache_size(Monitor *mon, const QDict *qdict)
  {
      int64_t value = qdict_get_int(qdict, "value");
diff --git a/hmp.h b/hmp.h
index 54cf71f..b6548a3 100644
--- a/hmp.h
+++ b/hmp.h
@@ -60,6 +60,7 @@ void hmp_drive_mirror(Monitor *mon, const QDict *qdict);
  void hmp_drive_backup(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_mc_delay(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);
diff --git a/qapi-schema.json b/qapi-schema.json
index e0a430c..2ed8098 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2135,6 +2135,19 @@
  { 'command': 'migrate_set_downtime', 'data': {'value': 'number'} }
##
+# @migrate-set-mc-delay
+#
+# Set delay (in milliseconds) between micro checkpoints.
+#
+# @value: maximum delay in milliseconds
+#
+# Returns: nothing on success
+#
+# Since: 1.6
+##
+{ 'command': 'migrate-set-mc-delay', 'data': {'value': 'int'} }
+
+##
  # @migrate_set_speed
  #
  # Set maximum speed for migration.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index fba15cd..6d7ef2f 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -754,6 +754,29 @@ Example:
  EQMP
{
+        .name       = "migrate-set-mc-delay",
+        .args_type  = "value:i",
+        .mhandler.cmd_new = qmp_marshal_input_migrate_set_mc_delay,
+    },
+
+SQMP
+migrate-set-mc-delay
+--------------------
+
+Set maximum delay (in milliseconds) between micro-checkpoints.
+
+Arguments:
+
+- "value": maximum delay (json-int)
+
+Example:
+
+-> { "execute": "migrate-set-mc-delay", "arguments": { "value": 100 } }
+<- { "return": {} }
+
+EQMP
+
+    {
          .name       = "client_migrate_info",
          .args_type  = 
"protocol:s,hostname:s,port:i?,tls-port:i?,cert-subject:s?",
          .params     = "protocol hostname port tls-port cert-subject",
diff --git a/vl.c b/vl.c
index 74d52ab..fa23d66 100644
--- a/vl.c
+++ b/vl.c
@@ -29,6 +29,7 @@
  #include <sys/time.h>
  #include <zlib.h>
  #include "qemu/bitmap.h"
+#include "migration/qemu-file.h"
/* Needed early for CONFIG_BSD etc. */
  #include "config-host.h"
@@ -4192,6 +4193,8 @@ int main(int argc, char **argv, char **envp)
      default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL);
+    register_savevm(NULL, "mc", -1, MC_VERSION, mc_info_save,
+                                mc_info_load, NULL);
if (nb_numa_nodes > 0) {
          int i;
--
1.8.1.2



That's a very good idea, I think - but we might get some pushback from the list.

There is a hesitation to add such low-level parameters, but for something like micro-checkpointing that may potentially have large impacts on application performance,
I do think it would be critical to expose more customizability
like 'set_migrate_parameter' to management software.

In fact, this separation of function may be "better" than continuing to expand
the list of individual commands in the QEMU monitor.

Could you submit a patch for the framework of such a command?

- Michael


- Michael




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