linux-kernel - Re: [PATCH RFC v1 0/2] vhost: ring format independence

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Message-ID: <20191012163635-mutt-send-email-mst@kernel.org>
Date:   Sat, 12 Oct 2019 16:36:56 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC v1 0/2] vhost: ring format independence

On Sat, Oct 12, 2019 at 03:31:50PM +0800, Jason Wang wrote:
> 
> On 2019/10/11 下午9:45, Michael S. Tsirkin wrote:
> > So the idea is as follows: we convert descriptors to an
> > independent format first, and process that converting to
> > iov later.
> > 
> > The point is that we have a tight loop that fetches
> > descriptors, which is good for cache utilization.
> > This will also allow all kind of batching tricks -
> > e.g. it seems possible to keep SMAP disabled while
> > we are fetching multiple descriptors.
> > 
> > And perhaps more importantly, this is a very good fit for the packed
> > ring layout, where we get and put descriptors in order.
> > 
> > This patchset seems to already perform exactly the same as the original
> > code already based on a microbenchmark.  More testing would be very much
> > appreciated.
> > 
> > Biggest TODO before this first step is ready to go in is to
> > batch indirect descriptors as well.
> > 
> > Integrating into vhost-net is basically
> > s/vhost_get_vq_desc/vhost_get_vq_desc_batch/ -
> > or add a module parameter like I did in the test module.
> 
> 
> It would be better to convert vhost_net then I can do some benchmark on
> that.
> 
> Thanks

Sure, I post a small patch that does this.

> 
> > 
> > 
> > 
> > Michael S. Tsirkin (2):
> >    vhost: option to fetch descriptors through an independent struct
> >    vhost: batching fetches
> > 
> >   drivers/vhost/test.c  |  19 ++-
> >   drivers/vhost/vhost.c | 333 +++++++++++++++++++++++++++++++++++++++++-
> >   drivers/vhost/vhost.h |  20 ++-
> >   3 files changed, 365 insertions(+), 7 deletions(-)
> >