Re: [PATCH v7 3/5] migration: Add zero-copy parameter for QMP/HMP for Linux

[Juan Quintela <quintela@redhat.com>]

Leonardo Bras Soares Passos <leobras@redhat.com> wrote:
> On Wed, Jan 19, 2022 at 3:16 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
>>
>> On Wed, Jan 19, 2022 at 03:03:29PM -0300, Leonardo Bras Soares Passos wrote:
>> > Hello Daniel,
>> >
>> > On Thu, Jan 13, 2022 at 10:10 AM Daniel P. Berrangé <berrange@redhat.com> wrote:
>> > >
>> > > On Thu, Jan 06, 2022 at 07:13:40PM -0300, Leonardo Bras wrote:
>> > > > Add property that allows zero-copy migration of memory pages,
>> > > > and also includes a helper function migrate_use_zero_copy() to check
>> > > > if it's enabled.
>> > > >
>> > > > No code is introduced to actually do the migration, but it allow
>> > > > future implementations to enable/disable this feature.
>> > > >
>> > > > On non-Linux builds this parameter is compiled-out.
>> > > >
>> > > > Signed-off-by: Leonardo Bras <leobras@redhat.com>
>> > > > ---
>> > > >  qapi/migration.json   | 24 ++++++++++++++++++++++++
>> > > >  migration/migration.h |  5 +++++
>> > > >  migration/migration.c | 32 ++++++++++++++++++++++++++++++++
>> > > >  migration/socket.c    |  5 +++++
>> > > >  monitor/hmp-cmds.c    |  6 ++++++
>> > > >  5 files changed, 72 insertions(+)
>> > >
>> > > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>> >
>> > Thanks!
>>
>
> Ok, I see the point.
> I will try to refactor the code changing zero-copy to zero-copy-send
> or something like that.

Hi

I am late to the party, but I agree with Dan that we need two flags.

Thre reason is that you can be the target of one migration, and later be
the source of a next one.  If we only have one flag that means different
things on the source and destination side, things become really
complicated.

Later, Juan.