From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: Understanding lock contention in __udp4_lib_mcast_deliver Date: Thu, 27 Jun 2013 12:58:39 -0700 Message-ID: <51CC996F.3020507@hp.com> References: <20130627192218.GA5936@sbohrermbp13-local.rgmadvisors.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Shawn Bohrer Return-path: Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:25248 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754565Ab3F0T6l (ORCPT ); Thu, 27 Jun 2013 15:58:41 -0400 In-Reply-To: <20130627192218.GA5936@sbohrermbp13-local.rgmadvisors.com> Sender: netdev-owner@vger.kernel.org List-ID: On 06/27/2013 12:22 PM, Shawn Bohrer wrote: > I'm looking for opportunities to improve the multicast receive > performance for our application, and I thought I'd spend some time > trying to understand what I thought might be a small/simple > improvement. Profiling with perf I see that there is spin_lock > contention in __udp4_lib_mcast_deliver: > > 0.68% swapper [kernel.kallsyms] [k] _raw_spin_lock > | > --- _raw_spin_lock > | > |--24.13%-- perf_adjust_freq_unthr_context.part.21 > | > |--22.40%-- scheduler_tick > | > |--14.96%-- __udp4_lib_mcast_deliver Are there other processes showing _raw_spin_lock time? It may be more clear to add a --sort symbol,dso or some such to your perf report command. Because what you show there suggests less than 1% of the active cycles are in _raw_spin_lock. rick jones