On Wed, May 31, 2023 at 11:32 AM Jason Wang <jasow...@redhat.com> wrote:
>
> On Wed, May 31, 2023 at 11:17 AM Jon Kohler <j...@nutanix.com> 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 <j...@nutanix.com>
>
> 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
More thought, if the performance boost only after fb3f903769e8, we
probably need to disable it by default and let the mgmt layer to
enable it.
Thanks
>
> 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)
> >
