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

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Message-ID: <20191011134358.16912-1-mst@redhat.com>
Date:   Fri, 11 Oct 2019 09:45:54 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>
Subject: [PATCH RFC v1 0/2] vhost: ring format independence

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.

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(-)

-- 
MST