netdev - Re: [PATCH bpf-next] xsk: introduce padding between ring pointers

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Message-ID: <169cf549-1adc-0b75-4fc1-52d2a110a6a7@iogearbox.net>
Date:   Tue, 13 Oct 2020 00:28:35 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Magnus Karlsson <magnus.karlsson@...il.com>
Cc:     "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        bpf <bpf@...r.kernel.org>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH bpf-next] xsk: introduce padding between ring pointers

On 10/12/20 1:13 PM, Magnus Karlsson wrote:
[...]
> Nope, that was a bad idea. After measuring, this one produces worse
> performance than the original suggestion with padding in between all
> members. Cannot explain why at the moment, but the numbers are
> convincing and above noise level for sure. So let us keep this one:
> 
> u32 producer ____cacheline_aligned_in_smp;
> ____cacheline_padding_in_smp;
> u32 consumer ____cacheline_aligned_in_smp;
> ____cacheline_padding_in_smp;
> u32 flags ____cacheline_aligned_in_smp;
> ____cacheline_padding_in_smp;
> 
>>> Do you want to submit a patch, or shall I do it? I like your
>>> ____cacheline_padding_in_smp better than my explicit "padN" member.

Ok, feel free to go for it.

Thanks,
Daniel