From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B01BFC282CE for ; Tue, 4 Jun 2019 10:07:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 84C3124C1B for ; Tue, 4 Jun 2019 10:07:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727134AbfFDKHv (ORCPT ); Tue, 4 Jun 2019 06:07:51 -0400 Received: from mga07.intel.com ([134.134.136.100]:59677 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726982AbfFDKHv (ORCPT ); Tue, 4 Jun 2019 06:07:51 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jun 2019 03:07:50 -0700 X-ExtLoop1: 1 Received: from shbuild888.sh.intel.com (HELO localhost) ([10.239.147.114]) by FMSMGA003.fm.intel.com with ESMTP; 04 Jun 2019 03:07:49 -0700 Date: Tue, 4 Jun 2019 18:07:35 +0800 From: Feng Tang To: Eric Dumazet Cc: kernel test robot , Stephen Rothwell , Willem de Bruijn , Soheil Hassas Yeganeh , LKML , "lkp@01.org" , "David S. Miller" , ying.huang@intel.com Subject: Re: [LKP] [tcp] 8b27dae5a2: netperf.Throughput_Mbps -25.7% regression Message-ID: <20190604100735.s2g3tc35ofybimek@shbuild888> References: <20190403063436.GG20952@shao2-debian> <20190530103048.hfld4t4m37jsg4yo@shbuild888> <20190530152314.ise5ycz6sdwfygph@shbuild888> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190530152314.ise5ycz6sdwfygph@shbuild888> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 30, 2019 at 11:23:14PM +0800, Feng Tang wrote: > Hi Eric, > > On Thu, May 30, 2019 at 05:21:40AM -0700, Eric Dumazet wrote: > > On Thu, May 30, 2019 at 3:31 AM Feng Tang wrote: > > > > > > On Wed, Apr 03, 2019 at 02:34:36PM +0800, kernel test robot wrote: > > > > Greeting, > > > > > > > > FYI, we noticed a -25.7% regression of netperf.Throughput_Mbps due to commit: > > > > > > > > > > > > commit: 8b27dae5a2e89a61c46c6dbc76c040c0e6d0ed4c ("tcp: add one skb cache for rx") > > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master > > > > > > Hi Eric, > > > > > > Could you help to check this? thanks, > > > > > > > Hmmm... patch is old and had some bugs that have been fixed. > > > > What numbers do you have with more recent kernels ? > > > I just run the test with 5.2-rc2, and the regression is still there. Hi Eric, Any hint on this? >From the perf data, the spinlock contention has an obvious increase: 9.28 +7.6 16.91 perf-profile.calltrace.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock.free_one_page.__free_pages_ok.___pskb_trim 18.55 +8.6 27.14 perf-profile.calltrace.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock_irqsave.get_page_from_freelist.__alloc_pages_nodemask.skb_page_frag_refill And for commit 8b27dae5a2 ("tcp: add one skb cache for rx"), IIUC, it is not a real cache like the "tx skb cache" patch, and kind of a delayed freeing. Thanks, Feng