From:   Jesper Dangaard Brouer <jbrouer@redhat.com>
Message-ID: <22ca47ca-325f-f4df-af5d-344be6b372d8@redhat.com>
Date:   Fri, 3 Mar 2023 11:39:06 +0100
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Cc:     brouer@redhat.com,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Larysa Zaremba <larysa.zaremba@intel.com>,
        =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@redhat.com>,
        Song Liu <song@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>, bpf@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v1 0/2] xdp: recycle Page Pool backed skbs built
 from XDP frames
Content-Language: en-US
To:     Alexander Lobakin <aleksander.lobakin@intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>
References: <20230301160315.1022488-1-aleksander.lobakin@intel.com>
In-Reply-To: <20230301160315.1022488-1-aleksander.lobakin@intel.com>
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On 01/03/2023 17.03, Alexander Lobakin wrote:
> Yeah, I still remember that "Who needs cpumap nowadays" (c), but anyway.
> 
> __xdp_build_skb_from_frame() missed the moment when the networking stack
> became able to recycle skb pages backed by a Page Pool. This was making
                                                ^^^^^^^^^
When talking about page_pool, can we write "page_pool" instead of
capitalized "Page Pool", please. I looked through the git log, and here
we all used "page_pool".

> e.g. cpumap redirect even less effective than simple %XDP_PASS. veth was
> also affected in some scenarios.

Thanks for working on closing this gap :-)

> A lot of drivers use skb_mark_for_recycle() already, it's been almost
> two years and seems like there are no issues in using it in the generic
> code too. {__,}xdp_release_frame() can be then removed as it losts its
> last user.
> Page Pool becomes then zero-alloc (or almost) in the abovementioned
> cases, too. Other memory type models (who needs them at this point)
> have no changes.
> 
> Some numbers on 1 Xeon Platinum core bombed with 27 Mpps of 64-byte
> IPv6 UDP:

What NIC driver?

> 
> Plain %XDP_PASS on baseline, Page Pool driver:
> 
> src cpu Rx     drops  dst cpu Rx
>    2.1 Mpps       N/A    2.1 Mpps
> 
> cpumap redirect (w/o leaving its node) on baseline:
> 
>    6.8 Mpps  5.0 Mpps    1.8 Mpps
> 
> cpumap redirect with skb PP recycling:
> 
>    7.9 Mpps  5.7 Mpps    2.2 Mpps   +22%
> 

It is of cause awesome, that cpumap SKBs are faster than normal SKB path.
I do wonder where the +22% number comes from?

> Alexander Lobakin (2):
>    xdp: recycle Page Pool backed skbs built from XDP frames
>    xdp: remove unused {__,}xdp_release_frame()
> 
>   include/net/xdp.h | 29 -----------------------------
>   net/core/xdp.c    | 19 ++-----------------
>   2 files changed, 2 insertions(+), 46 deletions(-)
>