On Wed, May 31, 2023 at 11:17 AM Jon Kohler <[email protected]> wrote:
>
> If kernel supports IFF_NAPI, lets use it, which is especially useful
> on kernels containing fb3f903769e8 ("tun: support NAPI for packets
> received from batched XDP buffs"), as IFF_NAPI allows the
> vhost_tx_batch path to use NAPI on XDP buffs.
>
> Benchmark w/ iperf -c (remote srv) -P (thread count) -l (stream size)
> from a guest running kernel 5.10.105 to remote bare metal running
> patched code on kernel 5.10.139. Guests were configured 1x virtio-net
> device with 4x queues, resulting in 4x vhost-worker threads. Hosts are
> identical with Intel ICX 4314 @ 2.4 GHz with Mellanox CX5 25GbE NIC ->
> Arista 25GbE switch. vhost-worker threads largely maxed out on CPU on
> "Before" and around ~50-60% utilization "After".
>
> Single Stream: iperf -P 1
> iperf -l size | Before | After | Increase
> 64B | 593 Mbits/sec | 712 Mbits/sec | ~20%
> 128B | 1.00 Gbits/sec | 1.18 Gbits/sec | ~18%
> 4KB | 17.6 Gbits/sec | 22.7 Gbits/sec | ~29%
>
> Multiple Stream: iperf -P 12
> iperf -l size | Before | After | Increase
> 64B | 6.35 Gbits/sec | 7.78 Gbits/sec | ~23%
> 128B | 10.8 Gbits/sec | 14.2 Gbits/sec | ~31%
> 4KB | 23.6 Gbits/sec | 23.6 Gbits/sec | (line speed)
>
> Signed-off-by: Jon Kohler <[email protected]>
Great, but I would suggest having an option.
So we can:
1) ease the debug and compare
2) enable this by default only for 8.1, disable it for pre 8.1
Thanks
Thanks
> ---
> net/tap-linux.c | 4 ++++
> net/tap-linux.h | 1 +
> 2 files changed, 5 insertions(+)
>
> diff --git a/net/tap-linux.c b/net/tap-linux.c
> index f54f308d359..fd94df166e0 100644
> --- a/net/tap-linux.c
> +++ b/net/tap-linux.c
> @@ -62,6 +62,10 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
> ifr.ifr_flags |= IFF_ONE_QUEUE;
> }
>
> + if (features & IFF_NAPI) {
> + ifr.ifr_flags |= IFF_NAPI;
> + }
> +
> if (*vnet_hdr) {
> if (features & IFF_VNET_HDR) {
> *vnet_hdr = 1;
> diff --git a/net/tap-linux.h b/net/tap-linux.h
> index bbbb62c2a75..f4d8e55270b 100644
> --- a/net/tap-linux.h
> +++ b/net/tap-linux.h
> @@ -37,6 +37,7 @@
>
> /* TUNSETIFF ifr flags */
> #define IFF_TAP 0x0002
> +#define IFF_NAPI 0x0010
> #define IFF_NO_PI 0x1000
> #define IFF_ONE_QUEUE 0x2000
> #define IFF_VNET_HDR 0x4000
> --
> 2.30.1 (Apple Git-130)
>
