Messages in this thread | | | Date | Mon, 11 Mar 2019 11:14:13 -0700 (PDT) | Subject | Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() | From | David Miller <> |
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From: "Michael S. Tsirkin" <mst@redhat.com> Date: Mon, 11 Mar 2019 09:59:28 -0400
> On Mon, Mar 11, 2019 at 03:13:17PM +0800, Jason Wang wrote: >> >> On 2019/3/8 下午10:12, Christoph Hellwig wrote: >> > On Wed, Mar 06, 2019 at 02:18:07AM -0500, 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. This is done through setup kernel address through vmap() and >> > > resigter MMU notifier for invalidation. >> > > >> > > Test shows about 24% improvement on TX PPS. TCP_STREAM doesn't see >> > > obvious improvement. >> > How is this going to work for CPUs with virtually tagged caches? >> >> >> Anything different that you worry? > > If caches have virtual tags then kernel and userspace view of memory > might not be automatically in sync if they access memory > through different virtual addresses. You need to do things like > flush_cache_page, probably multiple times.
"flush_dcache_page()"
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