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Date:   Mon, 3 Oct 2022 12:49:51 +0000
From:   Shenwei Wang <shenwei.wang@....com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Andrew Lunn <andrew@...n.ch>
CC:     "brouer@...hat.com" <brouer@...hat.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: RE: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support

Hi Jesper,

> >> On mvneta driver/platform we saw huge speedup replacing:
> >>
> >>     page_pool_release_page(rxq->page_pool, page); with
> >>     skb_mark_for_recycle(skb);
> >>

After replacing the page_pool_release_page with the skb_mark_for_recycle, I found something confused me a little in the testing result.
I tested with the sample app of "xdpsock" under two modes:  1. Native (xdpsock -i eth0). 2. Skb-mode (xdpsock -S -i eth0). 
The following are the testing result:
			With page_pool_release_page  (pps)                                           With skb_mark_for_recycle (pps)

   SKB-Mode                                  90K                                                                                                     200K       
   Native                                         190K                                                                                                   190K

The skb_mark_for_recycle solution boosted the performance of SKB-Mode to 200K+ PPS. That is even higher than the 
performance of Native solution.  Is this result reasonable? Do you have any clue why the SKB-Mode performance can 
go higher than that of Native one?

Thanks,
Shenwei



> -----Original Message-----
> From: Jesper Dangaard Brouer <jbrouer@...hat.com>
> Sent: Thursday, September 29, 2022 1:55 PM
> To: Shenwei Wang <shenwei.wang@....com>; Jesper Dangaard Brouer
> <jbrouer@...hat.com>; Andrew Lunn <andrew@...n.ch>
> Cc: brouer@...hat.com; Joakim Zhang <qiangqing.zhang@....com>; David S.
> Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Jakub
> Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Alexei
> Starovoitov <ast@...nel.org>; Daniel Borkmann <daniel@...earbox.net>;
> Jesper Dangaard Brouer <hawk@...nel.org>; John Fastabend
> <john.fastabend@...il.com>; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org; imx@...ts.linux.dev
> Subject: Re: [EXT] Re: [PATCH 1/1] net: fec: add initial XDP support
> 
> Caution: EXT Email
> 
> On 29/09/2022 17.52, Shenwei Wang wrote:
> >
> >> From: Jesper Dangaard Brouer <jbrouer@...hat.com>
> >>
> >> On 29/09/2022 15.26, Shenwei Wang wrote:
> >>>
> >>>> From: Andrew Lunn <andrew@...n.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:
> 
> Thanks for doing this! :-)
> 
> > 1. original implementation
> >
> > shenwei@...0:~$ 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@...0:~$ 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@...0:~$ 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
> 
> This is a very significant performance improvement (page pool with
> skb_mark_for_recycle).  This is very close to the max goodput for a 1Gbit/s link.
> 
> 
> > For small packet size (64 bytes), all three cases have almost the same result:
> >
> 
> To me this indicate, that the DMA map/unmap operations on this platform are
> indeed more expensive on larger packets.  Given this is what page_pool does,
> keeping the DMA mapping intact when recycling.
> 
> Driver still need DMA-sync, although I notice you set page_pool feature flag
> PP_FLAG_DMA_SYNC_DEV, this is good as page_pool will try to reduce sync size
> where possible. E.g. in this SKB case will reduce the DMA-sync to the
> max_len=FEC_ENET_RX_FRSIZE which should also help on performance.
> 
> 
> > shenwei@...0:~$ 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
> >

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