netdev - Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap()

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Date:   Mon, 11 Mar 2019 15:13:17 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterx@...hat.com,
        linux-mm@...ck.org, aarcange@...hat.com,
        linux-arm-kernel@...ts.infradead.org, linux-parisc@...r.kernel.org
Subject: Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through
 vmap()


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? I can have a test but do you know any 
archs that use virtual tag cache?

Thanks