RE: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support

Shenwei Wang
2022-09-29T15:52:54Z

> -----Original Message-----
> From: Jesper Dangaard Brouer <jbrouer@redhat.com>
> Sent: Thursday, September 29, 2022 10:29 AM
> To: Shenwei Wang <shenwei.wang@nxp.com>; Andrew Lunn <andrew@lunn.ch>
> Cc: brouer@redhat.com; Joakim Zhang <qiangqing.zhang@nxp.com>; David S.
> Miller <davem@davemloft.net>; Eric Dumazet <edumazet@google.com>; Jakub
> Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Alexei
> Starovoitov <ast@kernel.org>; Daniel Borkmann <daniel@iogearbox.net>;
> Jesper Dangaard Brouer <hawk@kernel.org>; John Fastabend
> <john.fastabend@gmail.com>; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; imx@lists.linux.dev
> Subject: Re: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support
>
> Caution: EXT Email
>
> On 29/09/2022 15.26, Shenwei Wang wrote:
> >
> >> From: Andrew Lunn <andrew@lunn.ch>
> >> Sent: Thursday, September 29, 2022 8:23 AM
> [...]
> >>
> >>> I actually did some compare testing regarding the page pool for
> >>> normal traffic. So far I don't see significant improvement in the
> >>> current implementation. The performance for large packets improves a
> >>> little, and the performance for small packets get a little worse.
> >>
> >> What hardware was this for? imx51? imx6? imx7 Vybrid? These all use the
> FEC.
> >
> > I tested on imx8qxp platform. It is ARM64.
>
> On mvneta driver/platform we saw huge speedup replacing:
>
> page_pool_release_page(rxq->page_pool, page); with
> skb_mark_for_recycle(skb);
>
> As I mentioned: Today page_pool have SKB recycle support (you might have
> looked at drivers that didn't utilize this yet), thus you don't need to release the
> page (page_pool_release_page) here. Instead you could simply mark the SKB
> for recycling, unless driver does some page refcnt tricks I didn't notice.
>
> On the mvneta driver/platform the DMA unmap (in page_pool_release_page)
> was very expensive. This imx8qxp platform might have faster DMA unmap in
> case is it cache-coherent.
>
> I would be very interested in knowing if skb_mark_for_recycle() helps on this
> platform, for normal network stack performance.
>

Did a quick compare testing for the following 3 scenarios:
1. original implementation

shenwei@5810:~$ iperf -c 10.81.16.245 -w 2m -i 1
------------------------------------------------------------
Client connecting to 10.81.16.245, TCP port 5001
TCP window size: 416 KByte (WARNING: requested 1.91 MByte)
------------------------------------------------------------
[ 1] local 10.81.17.20 port 49154 connected with 10.81.16.245 port 5001
[ ID] Interval Transfer Bandwidth
[ 1] 0.0000-1.0000 sec 104 MBytes 868 Mbits/sec
[ 1] 1.0000-2.0000 sec 105 MBytes 878 Mbits/sec
[ 1] 2.0000-3.0000 sec 105 MBytes 881 Mbits/sec
[ 1] 3.0000-4.0000 sec 105 MBytes 879 Mbits/sec
[ 1] 4.0000-5.0000 sec 105 MBytes 878 Mbits/sec
[ 1] 5.0000-6.0000 sec 105 MBytes 878 Mbits/sec
[ 1] 6.0000-7.0000 sec 104 MBytes 875 Mbits/sec
[ 1] 7.0000-8.0000 sec 104 MBytes 875 Mbits/sec
[ 1] 8.0000-9.0000 sec 104 MBytes 873 Mbits/sec
[ 1] 9.0000-10.0000 sec 104 MBytes 875 Mbits/sec
[ 1] 0.0000-10.0073 sec 1.02 GBytes 875 Mbits/sec

2. Page pool with page_pool_release_page

shenwei@5810:~$ iperf -c 10.81.16.245 -w 2m -i 1
------------------------------------------------------------
Client connecting to 10.81.16.245, TCP port 5001
TCP window size: 416 KByte (WARNING: requested 1.91 MByte)
------------------------------------------------------------
[ 1] local 10.81.17.20 port 35924 connected with 10.81.16.245 port 5001
[ ID] Interval Transfer Bandwidth
[ 1] 0.0000-1.0000 sec 101 MBytes 849 Mbits/sec
[ 1] 1.0000-2.0000 sec 102 MBytes 860 Mbits/sec
[ 1] 2.0000-3.0000 sec 102 MBytes 860 Mbits/sec
[ 1] 3.0000-4.0000 sec 102 MBytes 859 Mbits/sec
[ 1] 4.0000-5.0000 sec 103 MBytes 863 Mbits/sec
[ 1] 5.0000-6.0000 sec 103 MBytes 864 Mbits/sec
[ 1] 6.0000-7.0000 sec 103 MBytes 863 Mbits/sec
[ 1] 7.0000-8.0000 sec 103 MBytes 865 Mbits/sec
[ 1] 8.0000-9.0000 sec 103 MBytes 862 Mbits/sec
[ 1] 9.0000-10.0000 sec 102 MBytes 856 Mbits/sec
[ 1] 0.0000-10.0246 sec 1.00 GBytes 858 Mbits/sec

3. page pool with skb_mark_for_recycle

shenwei@5810:~$ iperf -c 10.81.16.245 -w 2m -i 1
------------------------------------------------------------
Client connecting to 10.81.16.245, TCP port 5001
TCP window size: 416 KByte (WARNING: requested 1.91 MByte)
------------------------------------------------------------
[ 1] local 10.81.17.20 port 42724 connected with 10.81.16.245 port 5001
[ ID] Interval Transfer Bandwidth
[ 1] 0.0000-1.0000 sec 111 MBytes 931 Mbits/sec
[ 1] 1.0000-2.0000 sec 112 MBytes 935 Mbits/sec
[ 1] 2.0000-3.0000 sec 111 MBytes 934 Mbits/sec
[ 1] 3.0000-4.0000 sec 111 MBytes 934 Mbits/sec
[ 1] 4.0000-5.0000 sec 111 MBytes 934 Mbits/sec
[ 1] 5.0000-6.0000 sec 112 MBytes 935 Mbits/sec
[ 1] 6.0000-7.0000 sec 111 MBytes 934 Mbits/sec
[ 1] 7.0000-8.0000 sec 111 MBytes 933 Mbits/sec
[ 1] 8.0000-9.0000 sec 112 MBytes 935 Mbits/sec
[ 1] 9.0000-10.0000 sec 111 MBytes 933 Mbits/sec
[ 1] 0.0000-10.0069 sec 1.09 GBytes 934 Mbits/sec

For small packet size (64 bytes), all three cases have almost the same result:

shenwei@5810:~$ iperf -c 10.81.16.245 -w 2m -i 1 -l 64
------------------------------------------------------------
Client connecting to 10.81.16.245, TCP port 5001
TCP window size: 416 KByte (WARNING: requested 1.91 MByte)
------------------------------------------------------------
[ 1] local 10.81.17.20 port 58204 connected with 10.81.16.245 port 5001
[ ID] Interval Transfer Bandwidth
[ 1] 0.0000-1.0000 sec 36.9 MBytes 309 Mbits/sec
[ 1] 1.0000-2.0000 sec 36.6 MBytes 307 Mbits/sec
[ 1] 2.0000-3.0000 sec 36.6 MBytes 307 Mbits/sec
[ 1] 3.0000-4.0000 sec 36.5 MBytes 307 Mbits/sec
[ 1] 4.0000-5.0000 sec 37.1 MBytes 311 Mbits/sec
[ 1] 5.0000-6.0000 sec 37.2 MBytes 312 Mbits/sec
[ 1] 6.0000-7.0000 sec 37.1 MBytes 311 Mbits/sec
[ 1] 7.0000-8.0000 sec 37.1 MBytes 311 Mbits/sec
[ 1] 8.0000-9.0000 sec 37.1 MBytes 312 Mbits/sec
[ 1] 9.0000-10.0000 sec 37.2 MBytes 312 Mbits/sec
[ 1] 0.0000-10.0097 sec 369 MBytes 310 Mbits/sec

Regards,
Shenwei

> >> By small packets, do you mean those under the copybreak limit?
> >>
> >> Please provide some benchmark numbers with your next patchset.
> >
> > Yes, the packet size is 64 bytes and it is under the copybreak limit.
> > As the impact is not significant, I would prefer to remove the
> > copybreak logic.
>
> +1 to removing this logic if possible, due to maintenance cost.
>
> --Jesper