From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC net-next] net ipv6: convert fib6_table rwlock to a percpu lock Date: Mon, 31 Jul 2017 16:10:07 -0700 Message-ID: <20170731161007.61c2d958@xeon-e3> References: <1a5ad2f0585aa66496b27e123d1c38b75552df4c.1501520674.git.shli@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, Kernel-team@fb.com, Shaohua Li , Wei Wang To: Shaohua Li Return-path: Received: from mail-pg0-f43.google.com ([74.125.83.43]:38855 "EHLO mail-pg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751217AbdGaXKJ (ORCPT ); Mon, 31 Jul 2017 19:10:09 -0400 Received: by mail-pg0-f43.google.com with SMTP id l64so89628pge.5 for ; Mon, 31 Jul 2017 16:10:09 -0700 (PDT) In-Reply-To: <1a5ad2f0585aa66496b27e123d1c38b75552df4c.1501520674.git.shli@fb.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 31 Jul 2017 10:18:57 -0700 Shaohua Li wrote: > From: Shaohua Li > > 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 You just reinvented brlock... RCU is not that hard, why not do it right?