netdev - Re: [RFC net-next] net ipv6: convert fib6

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Date:   Mon, 31 Jul 2017 16:10:07 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Shaohua Li <shli@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, Kernel-team@...com,
        Shaohua Li <shli@...com>, Wei Wang <weiwan@...gle.com>
Subject: Re: [RFC net-next] net ipv6: convert fib6_table rwlock to a percpu
 lock

On Mon, 31 Jul 2017 10:18:57 -0700
Shaohua Li <shli@...nel.org> wrote:

> From: Shaohua Li <shli@...com>
> 
> In a syn flooding test, the fib6_table rwlock is a significant
> bottleneck. While converting the rwlock to rcu sounds straighforward,
> but is very challenging if it's possible. A percpu spinlock is quite
> trival for this problem since updating the routing table is a rare
> event. In my test, the server receives around 1.5 Mpps in syn flooding
> test without the patch in a dual sockets and 56-CPU system. With the
> patch, the server receives around 3.8Mpps, and perf report doesn't show
> the locking issue.
> 
> Cc: Wei Wang <weiwan@...gle.com>

You just reinvented brlock...

RCU is not that hard, why not do it right?