netdev - [PATCH RFC v4 0/5] vhost: ring format independence

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Message-ID: <20191013113940.2863-1-mst@redhat.com>
Date:   Sun, 13 Oct 2019 07:41:55 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, Jason Wang <jasowang@...hat.com>
Subject: [PATCH RFC v4 0/5] vhost: ring format independence

This adds infrastructure required for supporting
multiple ring formats.

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.

This seems to perform exactly the same as the original
code already based on a microbenchmark.
Lightly tested.
More testing would be very much appreciated.

To use new code:
	echo 1 > /sys/module/vhost_test/parameters/newcode
or
	echo 1 > /sys/module/vhost_net/parameters/newcode

changes from v3:
        - fixed error handling in case of indirect descriptors
        - add BUG_ON to detect buffer overflow in case of bugs
                in response to comment by Jason Wang
        - minor code tweaks

Changes from v2:
	- fixed indirect descriptor batching
                reported by Jason Wang

Changes from v1:
	- typo fixes

Michael S. Tsirkin (5):
  vhost: option to fetch descriptors through an independent struct
  vhost/test: add an option to test new code
  vhost: batching fetches
  vhost/net: add an option to test new code
  vhost: last descriptor must have NEXT clear

 drivers/vhost/net.c   |  32 ++++-
 drivers/vhost/test.c  |  19 ++-
 drivers/vhost/vhost.c | 328 +++++++++++++++++++++++++++++++++++++++++-
 drivers/vhost/vhost.h |  20 ++-
 4 files changed, 385 insertions(+), 14 deletions(-)

-- 
MST