[PATCH] migration: Optimization about wait-unplug migration state

[PATCH] migration: Optimization about wait-unplug migration state

[Keqian Zhu]

qemu_savevm_nr_failover_devices() is originally designed to
get the number of failover devices, but it actually returns
the number of "unplug-pending" failover devices now. Moreover,
what drives migration state to wait-unplug should be the number
of "unplug-pending" failover devices, not all failover devices.

We can also notice that qemu_savevm_state_guest_unplug_pending()
and qemu_savevm_nr_failover_devices() is equivalent almost (from
the code view). So the latter is incorrect semantically and
useless, just delete it.

In the qemu_savevm_state_guest_unplug_pending(), once hit a
unplug-pending failover device, then it can return true right
now to save cpu time.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
---
Cc: jfreimann@redhat.com
Cc: Juan Quintela <quintela@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
---
 migration/migration.c |  2 +-
 migration/savevm.c    | 24 +++---------------------
 migration/savevm.h    |  1 -
 3 files changed, 4 insertions(+), 23 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 3a21a4686c..deedc968cf 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3333,7 +3333,7 @@ static void *migration_thread(void *opaque)
 
     qemu_savevm_state_setup(s->to_dst_file);
 
-    if (qemu_savevm_nr_failover_devices()) {
+    if (qemu_savevm_state_guest_unplug_pending()) {
         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                           MIGRATION_STATUS_WAIT_UNPLUG);
 
diff --git a/migration/savevm.c b/migration/savevm.c
index f19cb9ec7a..1d4220ece8 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1140,36 +1140,18 @@ void qemu_savevm_state_header(QEMUFile *f)
     }
 }
 
-int qemu_savevm_nr_failover_devices(void)
+bool qemu_savevm_state_guest_unplug_pending(void)
 {
     SaveStateEntry *se;
-    int n = 0;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (se->vmsd && se->vmsd->dev_unplug_pending &&
             se->vmsd->dev_unplug_pending(se->opaque)) {
-            n++;
-        }
-    }
-
-    return n;
-}
-
-bool qemu_savevm_state_guest_unplug_pending(void)
-{
-    SaveStateEntry *se;
-    int n = 0;
-
-    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
-        if (!se->vmsd || !se->vmsd->dev_unplug_pending) {
-            continue;
-        }
-        if (se->vmsd->dev_unplug_pending(se->opaque)) {
-            n++;
+            return true;
         }
     }
 
-    return n > 0;
+    return false;
 }
 
 void qemu_savevm_state_setup(QEMUFile *f)
diff --git a/migration/savevm.h b/migration/savevm.h
index c42b9c80ee..ba64a7e271 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -31,7 +31,6 @@
 
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_state_setup(QEMUFile *f);
-int qemu_savevm_nr_failover_devices(void);
 bool qemu_savevm_state_guest_unplug_pending(void);
 int qemu_savevm_state_resume_prepare(MigrationState *s);
 void qemu_savevm_state_header(QEMUFile *f);
-- 
2.19.1

Re: [PATCH] migration: Optimization about wait-unplug migration state

[Juan Quintela]

Keqian Zhu <zhukeqian1@huawei.com> wrote:
> qemu_savevm_nr_failover_devices() is originally designed to
> get the number of failover devices, but it actually returns
> the number of "unplug-pending" failover devices now. Moreover,
> what drives migration state to wait-unplug should be the number
> of "unplug-pending" failover devices, not all failover devices.
>
> We can also notice that qemu_savevm_state_guest_unplug_pending()
> and qemu_savevm_nr_failover_devices() is equivalent almost (from
> the code view). So the latter is incorrect semantically and
> useless, just delete it.
>
> In the qemu_savevm_state_guest_unplug_pending(), once hit a
> unplug-pending failover device, then it can return true right
> now to save cpu time.
>
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

For my reading you are right:
- 1st function naming is not right
- 2nd function achieves exactly the same effect

I will wait until Jens says anything, but then I will queue it.

Thanks, Juan.

Re: [PATCH] migration: Optimization about wait-unplug migration state

[zhukeqian]

On 2020/2/4 17:14, Juan Quintela wrote:
> Keqian Zhu <zhukeqian1@huawei.com> wrote:
>> qemu_savevm_nr_failover_devices() is originally designed to
>> get the number of failover devices, but it actually returns
>> the number of "unplug-pending" failover devices now. Moreover,
>> what drives migration state to wait-unplug should be the number
>> of "unplug-pending" failover devices, not all failover devices.
>>
>> We can also notice that qemu_savevm_state_guest_unplug_pending()
>> and qemu_savevm_nr_failover_devices() is equivalent almost (from
>> the code view). So the latter is incorrect semantically and
>> useless, just delete it.
>>
>> In the qemu_savevm_state_guest_unplug_pending(), once hit a
>> unplug-pending failover device, then it can return true right
>> now to save cpu time.
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> 
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> 
> For my reading you are right:
> - 1st function naming is not right
> - 2nd function achieves exactly the same effect
> 
> I will wait until Jens says anything, but then I will queue it.
> 
> Thanks, Juan.
> 
> 
> .
> 
Thanks,
Keqian.

Re: [PATCH] migration: Optimization about wait-unplug migration state

[Jens Freimann]

On Tue, Feb 04, 2020 at 01:08:41PM +0800, Keqian Zhu wrote:
>qemu_savevm_nr_failover_devices() is originally designed to
>get the number of failover devices, but it actually returns
>the number of "unplug-pending" failover devices now. Moreover,
>what drives migration state to wait-unplug should be the number
>of "unplug-pending" failover devices, not all failover devices.
>
>We can also notice that qemu_savevm_state_guest_unplug_pending()
>and qemu_savevm_nr_failover_devices() is equivalent almost (from
>the code view). So the latter is incorrect semantically and
>useless, just delete it.
>
>In the qemu_savevm_state_guest_unplug_pending(), once hit a
>unplug-pending failover device, then it can return true right
>now to save cpu time.
>
>Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
>---
>Cc: jfreimann@redhat.com
>Cc: Juan Quintela <quintela@redhat.com>
>Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>---
> migration/migration.c |  2 +-
> migration/savevm.c    | 24 +++---------------------
> migration/savevm.h    |  1 -
> 3 files changed, 4 insertions(+), 23 deletions(-)
>
>diff --git a/migration/migration.c b/migration/migration.c
>index 3a21a4686c..deedc968cf 100644
>--- a/migration/migration.c
>+++ b/migration/migration.c
>@@ -3333,7 +3333,7 @@ static void *migration_thread(void *opaque)
>
>     qemu_savevm_state_setup(s->to_dst_file);
>
>-    if (qemu_savevm_nr_failover_devices()) {
>+    if (qemu_savevm_state_guest_unplug_pending()) {
>         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
>                           MIGRATION_STATUS_WAIT_UNPLUG);
>
>diff --git a/migration/savevm.c b/migration/savevm.c
>index f19cb9ec7a..1d4220ece8 100644
>--- a/migration/savevm.c
>+++ b/migration/savevm.c
>@@ -1140,36 +1140,18 @@ void qemu_savevm_state_header(QEMUFile *f)
>     }
> }
>
>-int qemu_savevm_nr_failover_devices(void)
>+bool qemu_savevm_state_guest_unplug_pending(void)
> {
>     SaveStateEntry *se;
>-    int n = 0;
>
>     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>         if (se->vmsd && se->vmsd->dev_unplug_pending &&
>             se->vmsd->dev_unplug_pending(se->opaque)) {
>-            n++;
>-        }
>-    }
>-
>-    return n;
>-}
>-
>-bool qemu_savevm_state_guest_unplug_pending(void)
>-{
>-    SaveStateEntry *se;
>-    int n = 0;
>-
>-    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>-        if (!se->vmsd || !se->vmsd->dev_unplug_pending) {
>-            continue;
>-        }
>-        if (se->vmsd->dev_unplug_pending(se->opaque)) {
>-            n++;
>+            return true;
>         }
>     }
>
>-    return n > 0;
>+    return false;
> }
>
> void qemu_savevm_state_setup(QEMUFile *f)
>diff --git a/migration/savevm.h b/migration/savevm.h
>index c42b9c80ee..ba64a7e271 100644
>--- a/migration/savevm.h
>+++ b/migration/savevm.h
>@@ -31,7 +31,6 @@
>
> bool qemu_savevm_state_blocked(Error **errp);
> void qemu_savevm_state_setup(QEMUFile *f);
>-int qemu_savevm_nr_failover_devices(void);
> bool qemu_savevm_state_guest_unplug_pending(void);
> int qemu_savevm_state_resume_prepare(MigrationState *s);
> void qemu_savevm_state_header(QEMUFile *f);
>-- 
>2.19.1

Looks good to me. I tested it and it still works, so 

Tested-by: Jens Freimann <jfreimann@redhat.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com> 

regards
Jens

Re: [PATCH] migration: Optimization about wait-unplug migration state

[zhukeqian]

On 2020/2/5 22:40, Jens Freimann wrote:
> On Tue, Feb 04, 2020 at 01:08:41PM +0800, Keqian Zhu wrote:
>> qemu_savevm_nr_failover_devices() is originally designed to
>> get the number of failover devices, but it actually returns
>> the number of "unplug-pending" failover devices now. Moreover,
>> what drives migration state to wait-unplug should be the number
>> of "unplug-pending" failover devices, not all failover devices.
>>
>> We can also notice that qemu_savevm_state_guest_unplug_pending()
>> and qemu_savevm_nr_failover_devices() is equivalent almost (from
>> the code view). So the latter is incorrect semantically and
>> useless, just delete it.
>>
>> In the qemu_savevm_state_guest_unplug_pending(), once hit a
>> unplug-pending failover device, then it can return true right
>> now to save cpu time.
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
>> ---
>> Cc: jfreimann@redhat.com
>> Cc: Juan Quintela <quintela@redhat.com>
>> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>> ---
>> migration/migration.c |  2 +-
>> migration/savevm.c    | 24 +++---------------------
>> migration/savevm.h    |  1 -
>> 3 files changed, 4 insertions(+), 23 deletions(-)
>>
>> diff --git a/migration/migration.c b/migration/migration.c
>> index 3a21a4686c..deedc968cf 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -3333,7 +3333,7 @@ static void *migration_thread(void *opaque)
>>
>>     qemu_savevm_state_setup(s->to_dst_file);
>>
>> -    if (qemu_savevm_nr_failover_devices()) {
>> +    if (qemu_savevm_state_guest_unplug_pending()) {
>>         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
>>                           MIGRATION_STATUS_WAIT_UNPLUG);
>>
>> diff --git a/migration/savevm.c b/migration/savevm.c
>> index f19cb9ec7a..1d4220ece8 100644
>> --- a/migration/savevm.c
>> +++ b/migration/savevm.c
>> @@ -1140,36 +1140,18 @@ void qemu_savevm_state_header(QEMUFile *f)
>>     }
>> }
>>
>> -int qemu_savevm_nr_failover_devices(void)
>> +bool qemu_savevm_state_guest_unplug_pending(void)
>> {
>>     SaveStateEntry *se;
>> -    int n = 0;
>>
>>     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>>         if (se->vmsd && se->vmsd->dev_unplug_pending &&
>>             se->vmsd->dev_unplug_pending(se->opaque)) {
>> -            n++;
>> -        }
>> -    }
>> -
>> -    return n;
>> -}
>> -
>> -bool qemu_savevm_state_guest_unplug_pending(void)
>> -{
>> -    SaveStateEntry *se;
>> -    int n = 0;
>> -
>> -    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
>> -        if (!se->vmsd || !se->vmsd->dev_unplug_pending) {
>> -            continue;
>> -        }
>> -        if (se->vmsd->dev_unplug_pending(se->opaque)) {
>> -            n++;
>> +            return true;
>>         }
>>     }
>>
>> -    return n > 0;
>> +    return false;
>> }
>>
>> void qemu_savevm_state_setup(QEMUFile *f)
>> diff --git a/migration/savevm.h b/migration/savevm.h
>> index c42b9c80ee..ba64a7e271 100644
>> --- a/migration/savevm.h
>> +++ b/migration/savevm.h
>> @@ -31,7 +31,6 @@
>>
>> bool qemu_savevm_state_blocked(Error **errp);
>> void qemu_savevm_state_setup(QEMUFile *f);
>> -int qemu_savevm_nr_failover_devices(void);
>> bool qemu_savevm_state_guest_unplug_pending(void);
>> int qemu_savevm_state_resume_prepare(MigrationState *s);
>> void qemu_savevm_state_header(QEMUFile *f);
>> -- 
>> 2.19.1
> 
> Looks good to me. I tested it and it still works, so
> Tested-by: Jens Freimann <jfreimann@redhat.com>
> Reviewed-by: Jens Freimann <jfreimann@redhat.com>
> regards
> Jens
> 
> 
> .
> 
Thanks,
Keqian.