Re: [PATCH v3 0/3] QIOChannel async_write & async_flush + MSG_ZEROCOPY + multifd

[Leonardo Bras Soares Passos]

Hello Peter,

On Tue, Sep 28, 2021 at 7:51 PM Peter Xu <peterx@redhat.com> wrote:
>
> On Wed, Sep 22, 2021 at 07:24:20PM -0300, Leonardo Bras wrote:
> > This patch series intends to enable MSG_ZEROCOPY in QIOChannel, and make
> > use of it for multifd migration performance improvement.
> >
> > Patch #1 creates new callbacks for QIOChannel, allowing the implementation
> > of asynchronous writing.
> >
> > Patch #2 implements async_write and async_flush on QIOChannelSocket,
> >
> > Patch #3 Makes use of async_write + async_flush to enable MSG_ZEROCOPY
> > for migration using multifd nocomp.
> >
> > Results:
> > So far, the resource usage of __sys_sendmsg() reduced 15 times, and the
> > overall migration took 13-18% less time, based in synthetic workload.
> >
> > The objective is to reduce migration time in hosts with heavy cpu usage.
>
> My previous memory is that we'll add a capability bit for migration, so it'll
> not be enabled until user specified it.  Plan to do it in the next version?

You mean like I did in pre-V1, enabling ZEROCOPY for multifd it in QMP?
Or is this something else?


>
> It'll still be okay if you want to separate the work of (1) qio channel
> zero-copy support on sockets, and (2) apply zero copy to migration, then that
> can be done in part 2.  Your call. :)

Ok  :)

>
> Thanks,
>
> --
> Peter Xu
>

Thank you Peter,

Best regards,
Leonardo