Re: [Qemu-devel] [PATCH 09/12] ring: introduce lockless ring buffer

[Xiao Guangrong]

On 06/29/2018 12:23 PM, Michael S. Tsirkin wrote:
> On Thu, Jun 28, 2018 at 09:36:00PM +0800, Jason Wang wrote:
> > On 2018年06月04日 17:55, address@hidden wrote:
> > > From: Xiao Guangrong<address@hidden>

> > > Memory barrier is omitted here, please refer to the comment in the code.
> > >
> > > (1)https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/kfifo.h
> > > (2)http://dpdk.org/doc/api/rte__ring_8h.html
> > >
> > > Signed-off-by: Xiao Guangrong<address@hidden>
> > > ---
> >
> > May I ask why you need a MPSC ring here? Can we just use N SPSC ring for
> > submitting pages and another N SPSC ring for passing back results?
> >
> > Thanks
>
> Or just an SPSC ring + a lock.
> How big of a gain is lockless access to a trivial structure
> like the ring?

Okay, i will give a try.

BTW, we tried to use a global ring + lock for input and lockless ring for input,
the former did not show better performance. But we haven't tried to use global
ring + lock for out yet.