netdev - Re: [PATCH v2 net-next 2/6] bpf: Add percpu LRU list

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Date:   Mon, 14 Nov 2016 17:51:28 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v2 net-next 2/6] bpf: Add percpu LRU list

On Fri, Nov 11, 2016 at 10:55:07AM -0800, Martin KaFai Lau wrote:
> Instead of having a common LRU list, this patch allows a
> percpu LRU list which can be selected by specifying a map
> attribute.  The map attribute will be added in the later
> patch.
> 
> While the common use case for LRU is #reads >> #updates,
> percpu LRU list allows bpf prog to absorb unusual #updates
> under pathological case (e.g. external traffic facing machine which
> could be under attack).
> 
> Each percpu LRU is isolated from each other.  The LRU nodes (including
> free nodes) cannot be moved across different LRU Lists.
> 
> Here are the update performance comparison between
> common LRU list and percpu LRU list (the test code is
> at the last patch):
> 
> [root@...neltest003.31.prn1 ~]# for i in 1 4 8; do echo -n "$i cpus: "; \
> ./map_perf_test 16 $i | awk '{r += $3}END{print r " updates"}'; done
>  1 cpus: 2934082 updates
>  4 cpus: 7391434 updates
>  8 cpus: 6500576 updates
> 
> [root@...neltest003.31.prn1 ~]# for i in 1 4 8; do echo -n "$i cpus: "; \
> ./map_perf_test 32 $i | awk '{r += $3}END{printr " updates"}'; done
>   1 cpus: 2896553 updates
>   4 cpus: 9766395 updates
>   8 cpus: 17460553 updates
> 
> Signed-off-by: Martin KaFai Lau <kafai@...com>

Acked-by: Alexei Starovoitov <ast@...nel.org>