Re: [PATCH net-next 0/3] vhost: accelerate metadata access through vmap()

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 0/3] vhost: accelerate metadata access through vmap()
Date: Fri, 14 Dec 2018 10:16:08 -0500	[thread overview]
Message-ID: <20181214101356-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20181213101022.12475-1-jasowang@redhat.com>

On Thu, Dec 13, 2018 at 06:10:19PM +0800, Jason Wang wrote:
> Hi:
> 
> 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.
> 
> Test shows about 24% improvement on TX PPS. It should benefit other
> cases as well.

BTW if the issue is all the error checking, maybe we should
consider using something like uaccess_catch and check
in a single place.

> Please review
> 
> Jason Wang (3):
>   vhost: generalize adding used elem
>   vhost: fine grain userspace memory accessors
>   vhost: access vq metadata through kernel virtual address
> 
>  drivers/vhost/vhost.c | 281 ++++++++++++++++++++++++++++++++++++++----
>  drivers/vhost/vhost.h |  11 ++
>  2 files changed, 266 insertions(+), 26 deletions(-)
> 
> -- 
> 2.17.1