linux-kernel - Re: [PATCH net-next V4 0/6] switch to use tx skb array in tun

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Message-ID: <20160630184242-mutt-send-email-mst@redhat.com>
Date:	Thu, 30 Jun 2016 18:45:25 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	davem@...emloft.net, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, eric.dumazet@...il.com,
	brouer@...hat.com
Subject: Re: [PATCH net-next V4 0/6] switch to use tx skb array in tun

On Thu, Jun 30, 2016 at 02:45:30PM +0800, Jason Wang wrote:
> Hi all:
> 
> This series tries to switch to use skb array in tun. This is used to
> eliminate the spinlock contention between producer and consumer. The
> conversion was straightforward: just introdce a tx skb array and use
> it instead of sk_receive_queue.
> 
> A minor issue is to keep the tx_queue_len behaviour, since tun used to
> use it for the length of sk_receive_queue. This is done through:
> 
> - add the ability to resize multiple rings at once to avoid handling
>   partial resize failure for mutiple rings.
> - add the support for zero length ring.
> - introduce a notifier which was triggered when tx_queue_len was
>   changed for a netdev.
> - resize all queues during the tx_queue_len changing.
> 
> Tests shows about 15% improvement on guest rx pps:
> 
> Before: ~1300000pps
> After : ~1500000pps

Acked-by: Michael S. Tsirkin <mst@...hat.com>

Acked-from-altitude: 34697 feet.


> Changes from V3:
> - fix kbuild warnings
> - call NETDEV_CHANGE_TX_QUEUE_LEN on IFLA_TXQLEN
> 
> Changes from V2:
> - add multiple rings resizing support for ptr_ring/skb_array
> - add zero length ring support
> - introdce a NETDEV_CHANGE_TX_QUEUE_LEN
> - drop new flags
> 
> Changes from V1:
> - switch to use skb array instead of a customized circular buffer
> - add non-blocking support
> - rename .peek to .peek_len
> - drop lockless peeking since test show very minor improvement
> 
> Jason Wang (5):
>   ptr_ring: support zero length ring
>   skb_array: minor tweak
>   skb_array: add wrappers for resizing
>   net: introduce NETDEV_CHANGE_TX_QUEUE_LEN
>   tun: switch to use skb array for tx
> 
> Michael S. Tsirkin (1):
>   ptr_ring: support resizing multiple queues
> 
>  drivers/net/tun.c                | 138 ++++++++++++++++++++++++++++++++++++---
>  drivers/vhost/net.c              |  16 ++++-
>  include/linux/net.h              |   1 +
>  include/linux/netdevice.h        |   1 +
>  include/linux/ptr_ring.h         |  77 ++++++++++++++++++----
>  include/linux/skb_array.h        |  13 +++-
>  net/core/net-sysfs.c             |  15 ++++-
>  net/core/rtnetlink.c             |  16 +++--
>  tools/virtio/ringtest/ptr_ring.c |   5 ++
>  9 files changed, 255 insertions(+), 27 deletions(-)
> 
> -- 
> 2.7.4