On 28.07.2023 08:45, Michael S. Tsirkin wrote:

On Fri, Jul 28, 2023 at 01:26:23AM +0300, Arseniy Krasnov wrote:

quoted

Hello,

this patchset is first of three parts of another big patchset for
MSG_ZEROCOPY flag support:
https://lore.kernel.org/netdev/20230701063947.3422088-1-AVKrasnov@sberdevices.ru/ (local)

overall looks good. Two points I'd like to see addressed:

Thanks!

- what's the performance with all these changes - still same?

Yes, I perform quick tests and seems result are same. This is because last
implemented logic when I compare size of payload against 'num_max' is
for "emergency" case and not triggered in default environment. Anyway, I'll
perform retest at least in nested guest case.

- most systems have a copybreak scheme where buffers
  smaller than a given size are copied directly.
  This will address regression you see with small buffers -
  but need to find that value. we know it's between 4k and 32k :)

I see, You suggest to find this value and add this check for decision to
use zerocopy or copy ?

Thanks, Arseniy

quoted

During review of this series, Stefano Garzarella [off-list ref]
suggested to split it for three parts to simplify review and merging:

1) virtio and vhost updates (for fragged skbs) <--- this patchset
2) AF_VSOCK updates (allows to enable MSG_ZEROCOPY mode and read
   tx completions) and update for Documentation/.
3) Updates for tests and utils.

This series enables handling of fragged skbs in virtio and vhost parts.
Newly logic won't be triggered, because SO_ZEROCOPY options is still
impossible to enable at this moment (next bunch of patches from big
set above will enable it).

I've included changelog to some patches anyway, because there were some
comments during review of last big patchset from the link above.

Head for this patchset is 9d0cd5d25f7d45bce01bbb3193b54ac24b3a60f3

Link to v1:
https://lore.kernel.org/netdev/20230717210051.856388-1-AVKrasnov@sberdevices.ru/ (local)
Link to v2:
https://lore.kernel.org/netdev/20230718180237.3248179-1-AVKrasnov@sberdevices.ru/ (local)
Link to v3:
https://lore.kernel.org/netdev/20230720214245.457298-1-AVKrasnov@sberdevices.ru/ (local)

Changelog:
 * Patchset rebased and tested on new HEAD of net-next (see hash above).
 * See per-patch changelog after ---.

Arseniy Krasnov (4):
  vsock/virtio/vhost: read data from non-linear skb
  vsock/virtio: support to send non-linear skb
  vsock/virtio: non-linear skb handling for tap
  vsock/virtio: MSG_ZEROCOPY flag support

 drivers/vhost/vsock.c                   |  14 +-
 include/linux/virtio_vsock.h            |   6 +
 net/vmw_vsock/virtio_transport.c        |  79 +++++-
 net/vmw_vsock/virtio_transport_common.c | 312 ++++++++++++++++++------
 4 files changed, 330 insertions(+), 81 deletions(-)

-- 
2.25.1