Re: [PATCH net-next v8] virtio/vsock: replace virtio_vsock_pkt with sk_buff

[Stefano Garzarella]

On Thu, Dec 15, 2022 at 04:04:53AM -0500, Michael S. Tsirkin wrote:
> On Thu, Dec 15, 2022 at 09:47:57AM +0100, Stefano Garzarella wrote:
> > On Thu, Dec 15, 2022 at 04:36:44AM +0000, Bobby Eshleman wrote:
> > > This commit changes virtio/vsock to use sk_buff instead of
> > > virtio_vsock_pkt. Beyond better conforming to other net code, using
> > > sk_buff allows vsock to use sk_buff-dependent features in the future
> > > (such as sockmap) and improves throughput.
> > >
> > > This patch introduces the following performance changes:
> > >
> > > Tool/Config: uperf w/ 64 threads, SOCK_STREAM
> > > Test Runs: 5, mean of results
> > > Before: commit 95ec6bce2a0b ("Merge branch 'net-ipa-more-endpoints'")
> > >
> > > Test: 64KB, g2h
> > > Before: 21.63 Gb/s
> > > After: 25.59 Gb/s (+18%)
> > >
> > > Test: 16B, g2h
> > > Before: 11.86 Mb/s
> > > After: 17.41 Mb/s (+46%)
> > >
> > > Test: 64KB, h2g
> > > Before: 2.15 Gb/s
> > > After: 3.6 Gb/s (+67%)
> > >
> > > Test: 16B, h2g
> > > Before: 14.38 Mb/s
> > > After: 18.43 Mb/s (+28%)
> > >
> > > Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> > > ---
> > >
> > > Testing: passed vsock_test h2g and g2h
> > > Note2: net-next is closed, but sending out now in case more comments
> > > roll in, as discussed here:
> > > https://lore.kernel.org/all/Y34SoH1nFTXXLWbK@bullseye/
> > >
> > > Changes in v8:
> > > - vhost/vsock: remove unused enum
> > > - vhost/vsock: use spin_lock_bh() instead of spin_lock()
> > > - vsock/loopback: use __skb_dequeue instead of skb_dequeue
> > >
> > > Changes in v7:
> > > - use skb_queue_empty() instead of skb_queue_empty_lockless()
> > >
> > > Changes in v6:
> > > - use skb->cb instead of skb->_skb_refdst
> > > - use lock-free __skb_queue_purge for rx_queue when rx_lock held
> > >
> > > Changes in v5:
> > > - last_skb instead of skb: last_hdr->len = cpu_to_le32(last_skb->len)
> > >
> > > Changes in v4:
> > > - vdso/bits.h -> linux/bits.h
> > > - add virtio_vsock_alloc_skb() helper
> > > - virtio/vsock: rename buf_len -> total_len
> > > - update last_hdr->len
> > > - fix build_skb() for vsockmon (tested)
> > > - add queue helpers
> > > - use spin_{unlock/lock}_bh() instead of spin_lock()/spin_unlock()
> > > - note: I only ran a few g2h tests to check that this change
> > >  had no perf impact. The above data is still from patch
> > >  v3.
> > >
> > > Changes in v3:
> > > - fix seqpacket bug
> > > - use zero in vhost_add_used(..., 0) device doesn't write to buffer
> > > - use xmas tree style declarations
> > > - vsock_hdr() -> virtio_vsock_hdr() and other include file style fixes
> > > - no skb merging
> > > - save space by not using vsock_metadata
> > > - use _skb_refdst instead of skb buffer space for flags
> > > - use skb_pull() to keep track of read bytes instead of using an an
> > >  extra variable 'off' in the skb buffer space
> > > - remove unnecessary sk_allocation assignment
> > > - do not zero hdr needlessly
> > > - introduce virtio_transport_skb_len() because skb->len changes now
> > > - use spin_lock() directly on queue lock instead of sk_buff_head helpers
> > >  which use spin_lock_irqsave() (e.g., skb_dequeue)
> > > - do not reduce buffer size to be page size divisible
> > > - Note: the biggest performance change came from loosening the spinlock
> > >  variation and not reducing the buffer size.
> > >
> > > Changes in v2:
> > > - Use alloc_skb() directly instead of sock_alloc_send_pskb() to minimize
> > >  uAPI changes.
> > > - Do not marshal errors to -ENOMEM for non-virtio implementations.
> > > - No longer a part of the original series
> > > - Some code cleanup and refactoring
> > > - Include performance stats
> > >
> > > drivers/vhost/vsock.c                   | 213 +++++-------
> > > include/linux/virtio_vsock.h            | 126 +++++--
> > > net/vmw_vsock/virtio_transport.c        | 149 +++------
> > > net/vmw_vsock/virtio_transport_common.c | 422 +++++++++++++-----------
> > > net/vmw_vsock/vsock_loopback.c          |  51 +--
> > > 5 files changed, 495 insertions(+), 466 deletions(-)
> > >
> > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> > > index 5703775af129..ee0a00432cb1 100644
> > > --- a/drivers/vhost/vsock.c
> > > +++ b/drivers/vhost/vsock.c
> > > @@ -51,8 +51,7 @@ struct vhost_vsock {
> > > 	struct hlist_node hash;
> > >
> > > 	struct vhost_work send_pkt_work;
> > > -	spinlock_t send_pkt_list_lock;
> > > -	struct list_head send_pkt_list;	/* host->guest pending packets */
> > > +	struct sk_buff_head send_pkt_queue; /* host->guest pending packets */
> > >
> > > 	atomic_t queued_replies;
> > >
> > > @@ -108,40 +107,33 @@ vhost_transport_do_send_pkt(struct vhost_vsock
> > > *vsock,
> > > 	vhost_disable_notify(&vsock->dev, vq);
> > >
> > > 	do {
> > > -		struct virtio_vsock_pkt *pkt;
> > > +		struct virtio_vsock_hdr *hdr;
> > > +		size_t iov_len, payload_len;
> > > 		struct iov_iter iov_iter;
> > > +		u32 flags_to_restore = 0;
> > > +		struct sk_buff *skb;
> > > 		unsigned out, in;
> > > 		size_t nbytes;
> > > -		size_t iov_len, payload_len;
> > > 		int head;
> > > -		u32 flags_to_restore = 0;
> > >
> > > -		spin_lock_bh(&vsock->send_pkt_list_lock);
> > > -		if (list_empty(&vsock->send_pkt_list)) {
> > > -			spin_unlock_bh(&vsock->send_pkt_list_lock);
> > > +		spin_lock_bh(&vsock->send_pkt_queue.lock);
> > > +		skb = __skb_dequeue(&vsock->send_pkt_queue);
> > > +		spin_unlock_bh(&vsock->send_pkt_queue.lock);
> >
> > Sorry for coming late, but I just commented in Paolo's reply.
> > Here I think we can directly use the new virtio_vsock_skb_dequeue().
>
> Yea, pretty late.
> And using that will prevent me from merging this since it's not in my tree yet.
> We can do a cleanup patch on top.

Yep, sure!
Functionally nothing changes, so it's fine with a patch on top.

So, for this patch:

Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>

Thanks,
Stefano