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

[Peter Xu]

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?

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. :)

Thanks,

-- 
Peter Xu