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Message-ID: <3b00dc4a-b1b7-aa3f-c4ba-515138e4d6dd@redhat.com> Date: Tue, 12 Mar 2019 15:15:22 +0800 From: Jason Wang <jasowang@...hat.com> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: Andrea Arcangeli <aarcange@...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, Jerome Glisse <jglisse@...hat.com> Subject: Re: [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address On 2019/3/12 上午11:50, Michael S. Tsirkin wrote: >>>> Using direct mapping (I >>>> guess kernel will always try hugepage for that?) should be better and we can >>>> even use it for the data transfer not only for the metadata. >>>> >>>> Thanks >>> We can't really. The big issue is get user pages. Doing that on data >>> path will be slower than copyXuser. >> I meant if we can find a way to avoid doing gup in datapath. E.g vhost >> maintain a range tree and add or remove ranges through MMU notifier. Then in >> datapath, if we find the range, then use direct mapping otherwise >> copy_to_user(). >> >> Thanks > We can try. But I'm not sure there's any reason to think there's any > locality there. > Ok, but what kind of locality do you mean here? Thanks
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