Re: [Qemu-devel] [PATCH 02/15] colo-compare: implement the process of checkpoint

[Hailiang Zhang <zhang.zhanghailiang@huawei.com>]

Hi Jason,

On 2017/4/14 14:38, Jason Wang wrote:
>
> On 2017年04月14日 14:22, Hailiang Zhang wrote:
>> Hi Jason,
>>
>> On 2017/4/14 13:57, Jason Wang wrote:
>>> On 2017年02月22日 17:31, Zhang Chen wrote:
>>>> On 02/22/2017 11:42 AM, zhanghailiang wrote:
>>>>> While do checkpoint, we need to flush all the unhandled packets,
>>>>> By using the filter notifier mechanism, we can easily to notify
>>>>> every compare object to do this process, which runs inside
>>>>> of compare threads as a coroutine.
>>>> Hi~ Jason and Hailiang.
>>>>
>>>> I will send a patch set later about colo-compare notify mechanism for
>>>> Xen like this patch.
>>>> I want to add a new chardev socket way in colo-comapre connect to Xen
>>>> colo, for notify
>>>> checkpoint or failover, Because We have no choice to use this way
>>>> communicate with Xen codes.
>>>> That's means we will have two notify mechanism.
>>>> What do you think about this?
>>>>
>>>>
>>>> Thanks
>>>> Zhang Chen
>>> I was thinking the possibility of using similar way to for colo compare.
>>> E.g can we use socket? This can saves duplicated codes more or less.
>> Since there are too many sockets used by filter and COLO, (Two unix
>> sockets and two
>>   tcp sockets for each vNIC), I don't want to introduce more ;) , but
>> i'm not sure if it is
>> possible to make it more flexible and optional, abstract these
>> duplicated codes,
>> pass the opened fd (No matter eventfd or socket fd ) as parameter, for
>> example.
>> Is this way acceptable ?
>>
>> Thanks,
>> Hailiang
> Yes, that's kind of what I want. We don't want to use two message
> format. Passing a opened fd need management support, we still need a
> fallback if there's no management on top. For qemu/kvm, we can do all
> stuffs transparent to the cli by e.g socketpair() or others, but the key
> is to have a unified message format.

After a deeper investigation, i think we can re-use most codes, since there is no
existing way to notify xen (no ?), we still needs notify chardev socket (Be used to notify xen, it is optional.)
(http://patchwork.ozlabs.org/patch/733431/ "COLO-compare: Add Xen notify chardev socket handler frame")

Besides, there is an existing qmp comand 'xen-colo-do-checkpoint', we can re-use it to notify
colo-compare objects and other filter objects to do checkpoint, for the opposite direction, we use
the notify chardev socket (Only for xen).

So the codes will be like:
diff --git a/migration/colo.c b/migration/colo.c
index 91da936..813c281 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -224,7 +224,19 @@ ReplicationStatus *qmp_query_xen_replication_status(Error **errp)

  void qmp_xen_colo_do_checkpoint(Error **errp)
  {
+    Error *local_err = NULL;
+
      replication_do_checkpoint_all(errp);
+    /* Notify colo-compare and other filters to do checkpoint */
+    colo_notify_compares_event(NULL, COLO_CHECKPOINT, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+    colo_notify_filters_event(COLO_CHECKPOINT, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
  }

  static void colo_send_message(QEMUFile *f, COLOMessage msg,
diff --git a/net/colo-compare.c b/net/colo-compare.c
index 24e13f0..de975c5 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -391,6 +391,9 @@ static void colo_compare_inconsistent_notify(void)
  {
      notifier_list_notify(&colo_compare_notifiers,
                  migrate_get_current());
+    if (s->notify_dev) {
+       /* Do something, notify remote side through notify dev */
+    }
  }

  void colo_compare_register_notifier(Notifier *notify)

How about this scenario ？

> Thoughts?
>
> Thanks
>
>>> Thanks
>>>
>>>
>>> .
>>>
>>
>
> .
>