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    SubjectRe: [PATCH net-next V4 5/5] vhost: access vq metadata through kernel virtual address
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    On 2019/1/25 上午11:00, 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

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