Re: [RFC PATCH V3 0/5] Hi:

Michael S. Tsirkin
2019-01-07T03:28:56Z

On Mon, Jan 07, 2019 at 10:19:03AM +0800, Jason Wang wrote:
>
> On 2019/1/3 上午4:47, Michael S. Tsirkin wrote:
> > On Sat, Dec 29, 2018 at 08:46:51PM +0800, Jason Wang wrote:
> > > This series tries to access virtqueue metadata through kernel virtual
> > > address instead of copy_user() friends since they had too much
> > > overheads like checks, spec barriers or even hardware feature
> > > toggling.
> > Will review, thanks!
> > One questions that comes to mind is whether it's all about bypassing
> > stac/clac. Could you please include a performance comparison with
> > nosmap?
> >
>
> On machine without SMAP (Sandy Bridge):
>
> Before: 4.8Mpps
>
> After: 5.2Mpps

OK so would you say it's really unsafe versus safe accesses?
Or would you say it's just a better written code?

> On machine with SMAP (Broadwell):
>
> Before: 5.0Mpps
>
> After: 6.1Mpps
>
> No smap: 7.5Mpps
>
>
> Thanks

no smap being before or after?

--
MST