Re: [PATCH net-next V4 5/5] vhost: access vq metadata through kernel virtual address

From: Jason Wang
Date: Fri Jan 25 2019 - 04:16:53 EST



On 2019/1/25 äå11:00, Michael S. Tsirkin wrote:
On Thu, Jan 24, 2019 at 12:07:54PM +0800, Jason Wang wrote:
Meanwhile, could you pls post data comparing this last patch with the
below? This removes the speculation barrier replacing it with a
(useless but at least more lightweight) data dependency.
SMAP off

Your patch: 7.2MPPs

vmap: 7.4Mpps
OK so while we keep looking into vmap, why don't we merge something like
the below? Seems quite straight forward ...


The problem is it gives ~8% regression on PPS when SMAP is on. This is probably because the latency of lfence is hided by previous stac as mentioned in the commit b3bbfb3fb5d25776b8e3f361d2eedaabb0b496cd.

Thanks