diff mbox

[PULL,06/18] COLO: Introduce checkpointing protocol

Message ID 1477824430-1460-7-git-send-email-amit.shah@redhat.com
State New
Headers show

Commit Message

Amit Shah Oct. 30, 2016, 10:46 a.m. UTC
From: zhanghailiang <zhang.zhanghailiang@huawei.com>

We need communications protocol of user-defined to control
the checkpointing process.

The new checkpointing request is started by Primary VM,
and the interactive process like below:

Checkpoint synchronizing points:

                   Primary               Secondary
                                            initial work
'checkpoint-ready'    <-------------------- @

'checkpoint-request'  @ -------------------->
                                            Suspend (Only in hybrid mode)
'checkpoint-reply'    <-------------------- @
                      Suspend&Save state
'vmstate-send'        @ -------------------->
                      Send state            Receive state
'vmstate-received'    <-------------------- @
                      Release packets       Load state
'vmstate-load'        <-------------------- @
                      Resume                Resume (Only in hybrid mode)

                      Start Comparing (Only in hybrid mode)
NOTE:
 1) '@' who sends the message
 2) Every sync-point is synchronized by two sides with only
    one handshake(single direction) for low-latency.
    If more strict synchronization is required, a opposite direction
    sync-point should be added.
 3) Since sync-points are single direction, the remote side may
    go forward a lot when this side just receives the sync-point.
 4) For now, we only support 'periodic' checkpoint, for which
   the Secondary VM is not running, later we will support 'hybrid' mode.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Amit Shah <amit@amitshah.net>
---
 migration/colo.c       | 201 ++++++++++++++++++++++++++++++++++++++++++++++++-
 migration/trace-events |   2 +
 qapi-schema.json       |  25 ++++++
 3 files changed, 226 insertions(+), 2 deletions(-)

Comments

Eduardo Habkost Oct. 31, 2016, 6:25 p.m. UTC | #1
On Sun, Oct 30, 2016 at 04:16:58PM +0530, Amit Shah wrote:
[...]
> +static void colo_wait_handle_message(QEMUFile *f, int *checkpoint_request,
> +                                     Error **errp)
> +{
> +    COLOMessage msg;
> +    Error *local_err = NULL;
> +
> +    msg = colo_receive_message(f, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    switch (msg) {
> +    case COLO_MESSAGE_CHECKPOINT_REQUEST:
> +        *checkpoint_request = 1;
> +        break;
> +    default:
> +        *checkpoint_request = 0;
> +        error_setg(errp, "Got unknown COLO message: %d", msg);
> +        break;
> +    }
> +}
[...]
> +        colo_wait_handle_message(mis->from_src_file, &request, &local_err);
> +        if (local_err) {
> +            goto out;
> +        }
> +        assert(request);

GCC 4.8.5 doesn't seem to be smart enough to notice that request
will be always initialized:

  /root/qemu/migration/colo.c: In function ‘colo_process_incoming_thread’:
  /root/qemu/migration/colo.c:448:33: error: ‘request’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
           assert(request);
                                   ^
  cc1: all warnings being treated as errors

  $ gcc --version
  gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4)
Zhanghailiang Nov. 1, 2016, 1:48 a.m. UTC | #2
On 2016/11/1 2:25, Eduardo Habkost wrote:
> On Sun, Oct 30, 2016 at 04:16:58PM +0530, Amit Shah wrote:
> [...]
>> +static void colo_wait_handle_message(QEMUFile *f, int *checkpoint_request,
>> +                                     Error **errp)
>> +{
>> +    COLOMessage msg;
>> +    Error *local_err = NULL;
>> +
>> +    msg = colo_receive_message(f, &local_err);
>> +    if (local_err) {
>> +        error_propagate(errp, local_err);
>> +        return;
>> +    }
>> +
>> +    switch (msg) {
>> +    case COLO_MESSAGE_CHECKPOINT_REQUEST:
>> +        *checkpoint_request = 1;
>> +        break;
>> +    default:
>> +        *checkpoint_request = 0;
>> +        error_setg(errp, "Got unknown COLO message: %d", msg);
>> +        break;
>> +    }
>> +}
> [...]
>> +        colo_wait_handle_message(mis->from_src_file, &request, &local_err);
>> +        if (local_err) {
>> +            goto out;
>> +        }
>> +        assert(request);
>
> GCC 4.8.5 doesn't seem to be smart enough to notice that request
> will be always initialized:
>
>    /root/qemu/migration/colo.c: In function ‘colo_process_incoming_thread’:
>    /root/qemu/migration/colo.c:448:33: error: ‘request’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>             assert(request);
>                                     ^
>    cc1: all warnings being treated as errors
>
>    $ gcc --version
>    gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4)
>

Yes, you are right, Jeff has sent a patch to fix this
'[PATCH 1/1] migration: fix compiler warning on uninitialized variable'

Thanks,
Hailiang
diff mbox

Patch

diff --git a/migration/colo.c b/migration/colo.c
index 3a0d804..fcc9047 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -15,6 +15,7 @@ 
 #include "migration/colo.h"
 #include "trace.h"
 #include "qemu/error-report.h"
+#include "qapi/error.h"
 
 bool colo_supported(void)
 {
@@ -35,22 +36,147 @@  bool migration_incoming_in_colo_state(void)
     return mis && (mis->state == MIGRATION_STATUS_COLO);
 }
 
+static void colo_send_message(QEMUFile *f, COLOMessage msg,
+                              Error **errp)
+{
+    int ret;
+
+    if (msg >= COLO_MESSAGE__MAX) {
+        error_setg(errp, "%s: Invalid message", __func__);
+        return;
+    }
+    qemu_put_be32(f, msg);
+    qemu_fflush(f);
+
+    ret = qemu_file_get_error(f);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Can't send COLO message");
+    }
+    trace_colo_send_message(COLOMessage_lookup[msg]);
+}
+
+static COLOMessage colo_receive_message(QEMUFile *f, Error **errp)
+{
+    COLOMessage msg;
+    int ret;
+
+    msg = qemu_get_be32(f);
+    ret = qemu_file_get_error(f);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Can't receive COLO message");
+        return msg;
+    }
+    if (msg >= COLO_MESSAGE__MAX) {
+        error_setg(errp, "%s: Invalid message", __func__);
+        return msg;
+    }
+    trace_colo_receive_message(COLOMessage_lookup[msg]);
+    return msg;
+}
+
+static void colo_receive_check_message(QEMUFile *f, COLOMessage expect_msg,
+                                       Error **errp)
+{
+    COLOMessage msg;
+    Error *local_err = NULL;
+
+    msg = colo_receive_message(f, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+    if (msg != expect_msg) {
+        error_setg(errp, "Unexpected COLO message %d, expected %d",
+                          msg, expect_msg);
+    }
+}
+
+static int colo_do_checkpoint_transaction(MigrationState *s)
+{
+    Error *local_err = NULL;
+
+    colo_send_message(s->to_dst_file, COLO_MESSAGE_CHECKPOINT_REQUEST,
+                      &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    colo_receive_check_message(s->rp_state.from_dst_file,
+                    COLO_MESSAGE_CHECKPOINT_REPLY, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    /* TODO: suspend and save vm state to colo buffer */
+
+    colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    /* TODO: send vmstate to Secondary */
+
+    colo_receive_check_message(s->rp_state.from_dst_file,
+                       COLO_MESSAGE_VMSTATE_RECEIVED, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    colo_receive_check_message(s->rp_state.from_dst_file,
+                       COLO_MESSAGE_VMSTATE_LOADED, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    /* TODO: resume Primary */
+
+    return 0;
+out:
+    if (local_err) {
+        error_report_err(local_err);
+    }
+    return -EINVAL;
+}
+
 static void colo_process_checkpoint(MigrationState *s)
 {
+    Error *local_err = NULL;
+    int ret;
+
     s->rp_state.from_dst_file = qemu_file_get_return_path(s->to_dst_file);
     if (!s->rp_state.from_dst_file) {
         error_report("Open QEMUFile from_dst_file failed");
         goto out;
     }
 
+    /*
+     * Wait for Secondary finish loading VM states and enter COLO
+     * restore.
+     */
+    colo_receive_check_message(s->rp_state.from_dst_file,
+                       COLO_MESSAGE_CHECKPOINT_READY, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     qemu_mutex_lock_iothread();
     vm_start();
     qemu_mutex_unlock_iothread();
     trace_colo_vm_state_change("stop", "run");
 
-    /* TODO: COLO checkpoint savevm loop */
+    while (s->state == MIGRATION_STATUS_COLO) {
+        ret = colo_do_checkpoint_transaction(s);
+        if (ret < 0) {
+            goto out;
+        }
+    }
 
 out:
+    /* Throw the unreported error message after exited from loop */
+    if (local_err) {
+        error_report_err(local_err);
+    }
+
     if (s->rp_state.from_dst_file) {
         qemu_fclose(s->rp_state.from_dst_file);
     }
@@ -65,9 +191,33 @@  void migrate_start_colo_process(MigrationState *s)
     qemu_mutex_lock_iothread();
 }
 
+static void colo_wait_handle_message(QEMUFile *f, int *checkpoint_request,
+                                     Error **errp)
+{
+    COLOMessage msg;
+    Error *local_err = NULL;
+
+    msg = colo_receive_message(f, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    switch (msg) {
+    case COLO_MESSAGE_CHECKPOINT_REQUEST:
+        *checkpoint_request = 1;
+        break;
+    default:
+        *checkpoint_request = 0;
+        error_setg(errp, "Got unknown COLO message: %d", msg);
+        break;
+    }
+}
+
 void *colo_process_incoming_thread(void *opaque)
 {
     MigrationIncomingState *mis = opaque;
+    Error *local_err = NULL;
 
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_COLO);
@@ -85,9 +235,56 @@  void *colo_process_incoming_thread(void *opaque)
      */
     qemu_file_set_blocking(mis->from_src_file, true);
 
-    /* TODO: COLO checkpoint restore loop */
+    colo_send_message(mis->to_src_file, COLO_MESSAGE_CHECKPOINT_READY,
+                      &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    while (mis->state == MIGRATION_STATUS_COLO) {
+        int request;
+
+        colo_wait_handle_message(mis->from_src_file, &request, &local_err);
+        if (local_err) {
+            goto out;
+        }
+        assert(request);
+        /* FIXME: This is unnecessary for periodic checkpoint mode */
+        colo_send_message(mis->to_src_file, COLO_MESSAGE_CHECKPOINT_REPLY,
+                     &local_err);
+        if (local_err) {
+            goto out;
+        }
+
+        colo_receive_check_message(mis->from_src_file,
+                           COLO_MESSAGE_VMSTATE_SEND, &local_err);
+        if (local_err) {
+            goto out;
+        }
+
+        /* TODO: read migration data into colo buffer */
+
+        colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_RECEIVED,
+                     &local_err);
+        if (local_err) {
+            goto out;
+        }
+
+        /* TODO: load vm state */
+
+        colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_LOADED,
+                     &local_err);
+        if (local_err) {
+            goto out;
+        }
+    }
 
 out:
+    /* Throw the unreported error message after exited from loop */
+    if (local_err) {
+        error_report_err(local_err);
+    }
+
     if (mis->to_src_file) {
         qemu_fclose(mis->to_src_file);
     }
diff --git a/migration/trace-events b/migration/trace-events
index a29e5a0..f374c8c 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -210,3 +210,5 @@  migration_tls_incoming_handshake_complete(void) ""
 
 # migration/colo.c
 colo_vm_state_change(const char *old, const char *new) "Change '%s' => '%s'"
+colo_send_message(const char *msg) "Send '%s' message"
+colo_receive_message(const char *msg) "Receive '%s' message"
diff --git a/qapi-schema.json b/qapi-schema.json
index 8b21215..cafada8 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -787,6 +787,31 @@ 
 { 'command': 'migrate-start-postcopy' }
 
 ##
+# @COLOMessage
+#
+# The message transmission between Primary side and Secondary side.
+#
+# @checkpoint-ready: Secondary VM (SVM) is ready for checkpointing
+#
+# @checkpoint-request: Primary VM (PVM) tells SVM to prepare for checkpointing
+#
+# @checkpoint-reply: SVM gets PVM's checkpoint request
+#
+# @vmstate-send: VM's state will be sent by PVM.
+#
+# @vmstate-size: The total size of VMstate.
+#
+# @vmstate-received: VM's state has been received by SVM.
+#
+# @vmstate-loaded: VM's state has been loaded by SVM.
+#
+# Since: 2.8
+##
+{ 'enum': 'COLOMessage',
+  'data': [ 'checkpoint-ready', 'checkpoint-request', 'checkpoint-reply',
+            'vmstate-send', 'vmstate-size', 'vmstate-received',
+            'vmstate-loaded' ] }
+
 # @MouseInfo:
 #
 # Information about a mouse device.