Re: [Qemu-devel] [RFC PATCH v1: 11/12] mc: register MC qemu-file functions and expose MC tunable capability

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

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,
> mrhines@linux.vnet.ibm.com wrote:
>
>> From: "Michael R. Hines" <mrhines@us.ibm.com>
>>
>> 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 <mrhines@us.ibm.com>
>> ---
>>   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
>> +@item migrate_set_downtime @var{second}
>> +@findex 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