Re: [Qemu-devel] [PATCH] migration: calculate expected_downtime with ram_bytes_remaining()

[Balamuruhan S <bala24@linux.vnet.ibm.com>]

On 2018-04-10 15:22, Balamuruhan S wrote:
> On Wed, Apr 04, 2018 at 11:04:59AM +0200, Juan Quintela wrote:
>> Balamuruhan S <bala24@linux.vnet.ibm.com> wrote:
>> > expected_downtime value is not accurate with dirty_pages_rate * page_size,
>> > using ram_bytes_remaining would yeild it correct.
>> >
>> > Signed-off-by: Balamuruhan S <bala24@linux.vnet.ibm.com>
>> 
>> Reviewed-by: Juan Quintela <quintela@redhat.com>
>> 
>> See my other mail on the thread, my understanding is that your change 
>> is
>> corret (TM).
> 
> Juan, Please help to merge it.

Sorry for asking it as during discussion going on, but the reason is 
currently
postcopy migration for HP backed P8 guest from P8 -> P9 is broken and to 
use
precopy with appropriate downtime value we need this patch to be 
backported
to distros that is to be released soon.

> 
> Regards,
> Bala
> 
>> 
>> Thanks, Juan.
>> 
>> > ---
>> >  migration/migration.c | 3 +--
>> >  1 file changed, 1 insertion(+), 2 deletions(-)
>> >
>> > diff --git a/migration/migration.c b/migration/migration.c
>> > index 58bd382730..4e43dc4f92 100644
>> > --- a/migration/migration.c
>> > +++ b/migration/migration.c
>> > @@ -2245,8 +2245,7 @@ static void migration_update_counters(MigrationState *s,
>> >       * recalculate. 10000 is a small enough number for our purposes
>> >       */
>> >      if (ram_counters.dirty_pages_rate && transferred > 10000) {
>> > -        s->expected_downtime = ram_counters.dirty_pages_rate *
>> > -            qemu_target_page_size() / bandwidth;
>> > +        s->expected_downtime = ram_bytes_remaining() / bandwidth;
>> >      }
>> >
>> >      qemu_file_reset_rate_limit(s->to_dst_file);
>>