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: Tue, 1 Aug 2017 07:45:28 -0700 Message-ID: <20170801074528.289fc520@xeon-e3> References: <1a5ad2f0585aa66496b27e123d1c38b75552df4c.1501520674.git.shli@fb.com> <20170731161007.61c2d958@xeon-e3> <20170801025704.fuhxll23d3eenwrz@kernel.org> 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-f48.google.com ([74.125.83.48]:35880 "EHLO mail-pg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368AbdHAOpb (ORCPT ); Tue, 1 Aug 2017 10:45:31 -0400 Received: by mail-pg0-f48.google.com with SMTP id v77so3160181pgb.3 for ; Tue, 01 Aug 2017 07:45:31 -0700 (PDT) In-Reply-To: <20170801025704.fuhxll23d3eenwrz@kernel.org> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 31 Jul 2017 19:57:04 -0700 Shaohua Li wrote: > On Mon, Jul 31, 2017 at 04:10:07PM -0700, Stephen Hemminger wrote: > > 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... It was a long time ago (2.4) that brlock came in https://lwn.net/Articles/378781/ I removed it in 2.5.64 or so.