Re: [Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

[Dr. David Alan Gilbert]

* 858585 jemmy (jemmy858...@gmail.com) wrote:
> On Thu, Apr 12, 2018 at 12:43 AM, Dr. David Alan Gilbert
>  wrote:
> > * Lidong Chen (jemmy858...@gmail.com) wrote:
> >> After postcopy, the destination qemu work in the dedicated
> >> thread, so only invoke yield_until_fd_readable before postcopy
> >> migration.
> >
> > The subject line needs to be more discriptive:
> >migration: Stop rdma yielding during incoming postcopy
> >
> > I think.
> > (Also please check the subject spellings)
> >
> >> Signed-off-by: Lidong Chen 
> >> ---
> >>  migration/rdma.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/migration/rdma.c b/migration/rdma.c
> >> index 53773c7..81be482 100644
> >> --- a/migration/rdma.c
> >> +++ b/migration/rdma.c
> >> @@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext 
> >> *rdma)
> >>   * Coroutine doesn't start until migration_fd_process_incoming()
> >>   * so don't yield unless we know we're running inside of a coroutine.
> >>   */
> >> -if (rdma->migration_started_on_destination) {
> >> +if (rdma->migration_started_on_destination &&
> >> +migration_incoming_get_current()->state == 
> >> MIGRATION_STATUS_ACTIVE) {
> >
> > OK, that's a bit delicate; watch if it ever gets called in a failure
> > case or similar - and also wathc out if we make more use of the status
> > on the destination, but otherwise, and with a fix for the subject;
> 
> How about use migration_incoming_get_current()->have_listen_thread?

That's supposed to be pretty internal to the postcopy code, so I prefer
the status check.

Dave

> if (rdma->migration_started_on_destination &&
> migration_incoming_get_current()->have_listen_thread == false) {
> yield_until_fd_readable(rdma->comp_channel->fd);
> }
> 
> >
> >
> > Reviewed-by: Dr. David Alan Gilbert 
> >
> >>  yield_until_fd_readable(rdma->comp_channel->fd);
> >>  } else {
> >>  /* This is the source side, we're in a separate thread
> >>   * or destination prior to migration_fd_process_incoming()
> >> + * after postcopy, the destination also in a seprate thread.
> >>   * we can't yield; so we have to poll the fd.
> >>   * But we need to be able to handle 'cancel' or an error
> >>   * without hanging forever.
> >> --
> >> 1.8.3.1
> >>
> > --
> > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

[858585 jemmy]

On Thu, Apr 12, 2018 at 12:43 AM, Dr. David Alan Gilbert
 wrote:
> * Lidong Chen (jemmy858...@gmail.com) wrote:
>> After postcopy, the destination qemu work in the dedicated
>> thread, so only invoke yield_until_fd_readable before postcopy
>> migration.
>
> The subject line needs to be more discriptive:
>migration: Stop rdma yielding during incoming postcopy
>
> I think.
> (Also please check the subject spellings)
>
>> Signed-off-by: Lidong Chen 
>> ---
>>  migration/rdma.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/migration/rdma.c b/migration/rdma.c
>> index 53773c7..81be482 100644
>> --- a/migration/rdma.c
>> +++ b/migration/rdma.c
>> @@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext 
>> *rdma)
>>   * Coroutine doesn't start until migration_fd_process_incoming()
>>   * so don't yield unless we know we're running inside of a coroutine.
>>   */
>> -if (rdma->migration_started_on_destination) {
>> +if (rdma->migration_started_on_destination &&
>> +migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) 
>> {
>
> OK, that's a bit delicate; watch if it ever gets called in a failure
> case or similar - and also wathc out if we make more use of the status
> on the destination, but otherwise, and with a fix for the subject;

How about use migration_incoming_get_current()->have_listen_thread?

if (rdma->migration_started_on_destination &&
migration_incoming_get_current()->have_listen_thread == false) {
yield_until_fd_readable(rdma->comp_channel->fd);
}

>
>
> Reviewed-by: Dr. David Alan Gilbert 
>
>>  yield_until_fd_readable(rdma->comp_channel->fd);
>>  } else {
>>  /* This is the source side, we're in a separate thread
>>   * or destination prior to migration_fd_process_incoming()
>> + * after postcopy, the destination also in a seprate thread.
>>   * we can't yield; so we have to poll the fd.
>>   * But we need to be able to handle 'cancel' or an error
>>   * without hanging forever.
>> --
>> 1.8.3.1
>>
> --
> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

[Dr. David Alan Gilbert]

* Lidong Chen (jemmy858...@gmail.com) wrote:
> After postcopy, the destination qemu work in the dedicated
> thread, so only invoke yield_until_fd_readable before postcopy
> migration.

The subject line needs to be more discriptive:
   migration: Stop rdma yielding during incoming postcopy

I think.
(Also please check the subject spellings)

> Signed-off-by: Lidong Chen 
> ---
>  migration/rdma.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 53773c7..81be482 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext 
> *rdma)
>   * Coroutine doesn't start until migration_fd_process_incoming()
>   * so don't yield unless we know we're running inside of a coroutine.
>   */
> -if (rdma->migration_started_on_destination) {
> +if (rdma->migration_started_on_destination &&
> +migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {

OK, that's a bit delicate; watch if it ever gets called in a failure
case or similar - and also wathc out if we make more use of the status
on the destination, but otherwise, and with a fix for the subject;


Reviewed-by: Dr. David Alan Gilbert 

>  yield_until_fd_readable(rdma->comp_channel->fd);
>  } else {
>  /* This is the source side, we're in a separate thread
>   * or destination prior to migration_fd_process_incoming()
> + * after postcopy, the destination also in a seprate thread.
>   * we can't yield; so we have to poll the fd.
>   * But we need to be able to handle 'cancel' or an error
>   * without hanging forever.
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK

[Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

[Lidong Chen]

After postcopy, the destination qemu work in the dedicated
thread, so only invoke yield_until_fd_readable before postcopy
migration.

Signed-off-by: Lidong Chen 
---
 migration/rdma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/migration/rdma.c b/migration/rdma.c
index 53773c7..81be482 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext 
*rdma)
  * Coroutine doesn't start until migration_fd_process_incoming()
  * so don't yield unless we know we're running inside of a coroutine.
  */
-if (rdma->migration_started_on_destination) {
+if (rdma->migration_started_on_destination &&
+migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {
 yield_until_fd_readable(rdma->comp_channel->fd);
 } else {
 /* This is the source side, we're in a separate thread
  * or destination prior to migration_fd_process_incoming()
+ * after postcopy, the destination also in a seprate thread.
  * we can't yield; so we have to poll the fd.
  * But we need to be able to handle 'cancel' or an error
  * without hanging forever.
-- 
1.8.3.1