From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 00/16] Remove the ipv4 routing cache Date: Wed, 25 Jul 2012 16:39:39 -0700 (PDT) Message-ID: <20120725.163939.581743307449189972.davem@davemloft.net> References: <20120720.142502.1144557295933737451.davem@davemloft.net> <20120725.161732.91008692477078715.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org To: alexander.duyck@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:47049 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774Ab2GYXjk (ORCPT ); Wed, 25 Jul 2012 19:39:40 -0400 In-Reply-To: <20120725.161732.91008692477078715.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: From: David Miller Date: Wed, 25 Jul 2012 16:17:32 -0700 (PDT) > From: Alexander Duyck > Date: Wed, 25 Jul 2012 16:02:45 -0700 > >> Since your patches are in I have started to re-run my tests. I am >> seeing a significant drop in throughput with 8 flows which I expected, >> however it looks like one of the biggest issues I am seeing is that >> the dst_hold and dst_release calls seem to be causing some serious >> cache thrash. I was at 12.5Mpps w/ 8 flows before the patches, after >> your patches it drops to 8.3Mpps. > > Yes, this is something we knew would start happening. > > One idea is to make cached dsts be per-cpu in the nexthops. Actually I think what really kills your case is the removal of the noref path for route lookups. I'll work on a patch to restore that in the case where we use cached routes from the FIB nexthops.