Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755362Ab2JCNaI (ORCPT ); Wed, 3 Oct 2012 09:30:08 -0400 Received: from mailout-de.gmx.net ([213.165.64.23]:51005 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755241Ab2JCNaG (ORCPT ); Wed, 3 Oct 2012 09:30:06 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/nNBA1trfntFHdS6bIquaSsg0/ql+8adV9WHi3Zf 9dlrdtpuKCKt5b Message-ID: <1349271001.4465.66.camel@marge.simpson.net> Subject: Re: Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue() From: Mike Galbraith To: Mel Gorman Cc: Peter Zijlstra , Suresh Siddha , LKML Date: Wed, 03 Oct 2012 15:30:01 +0200 In-Reply-To: <1349251997.4465.42.camel@marge.simpson.net> References: <20121002065143.GK29125@suse.de> <1349164176.7086.43.camel@marge.simpson.net> <20121002084501.GL29125@suse.de> <1349170282.7086.56.camel@marge.simpson.net> <20121002131421.GN29125@suse.de> <1349247011.4465.24.camel@marge.simpson.net> <1349251997.4465.42.camel@marge.simpson.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3253 Lines: 53 On Wed, 2012-10-03 at 10:13 +0200, Mike Galbraith wrote: > Watching all cores instead. > > switch rate ~890KHz switch rate ~570KHz > NO_TTWU_QUEUE nohz=off TTWU_QUEUE nohz=off > 5.38% [kernel] [k] __schedule 4.81% [kernel] [k] _raw_spin_lock_irqsave > 4.29% [kernel] [k] _raw_spin_lock_irqsave 3.36% [kernel] [k] __skb_recv_datagram > 2.88% [kernel] [k] resched_task 2.71% [kernel] [k] copy_user_generic_string > 2.60% [kernel] [k] copy_user_generic_string 2.67% [kernel] [k] reschedule_interrupt > 2.38% [kernel] [k] __switch_to 2.62% [kernel] [k] sock_alloc_send_pskb > 2.15% [kernel] [k] sock_alloc_send_pskb 2.52% [kernel] [k] __schedule > 2.08% [kernel] [k] __skb_recv_datagram 2.31% [kernel] [k] try_to_wake_up > 1.81% [kernel] [k] udp_sendmsg 2.14% [kernel] [k] system_call > 1.76% [kernel] [k] system_call 1.98% [kernel] [k] udp_sendmsg > 1.73% [kernel] [k] __udp4_lib_lookup 1.96% [kernel] [k] __udp4_lib_lookup > 1.65% [kernel] [k] __slab_free.isra.42 1.78% [kernel] [k] sock_def_readable > 1.62% [kernel] [k] try_to_wake_up 1.63% [kernel] [k] __slab_free.isra.42 > 1.43% [kernel] [k] update_rq_clock 1.60% [kernel] [k] __switch_to > 1.43% [kernel] [k] sock_def_readable 1.52% [kernel] [k] dma_issue_pending_all > 1.41% [kernel] [k] dma_issue_pending_all 1.48% [kernel] [k] __ip_append_data.isra.35 > 1.40% [kernel] [k] menu_select 1.44% [kernel] [k] _raw_spin_lock > 1.36% [kernel] [k] finish_task_switch 1.38% [kernel] [k] _raw_spin_unlock_irqrestore > 1.30% [kernel] [k] ksize 1.33% [kernel] [k] __udp4_lib_rcv > > Strange. nohz=off, pipe-test with one half pinned to CPU0, the other to CPU1. procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st TTW_QUEUE 1 0 0 3039488 50948 444720 0 0 0 0 539724 1013417 1 15 84 0 0 1 0 0 3039488 50956 444720 0 0 0 1 540853 1015679 1 15 84 0 0 1 0 0 3039364 50956 444720 0 0 0 0 541630 1017239 1 16 83 0 0 2 0 0 3038992 50956 444720 0 0 0 0 335550 1096569 4 20 76 0 0 NO_TTWU_QUEUE 1 0 0 3038992 50956 444720 0 0 0 0 33100 1318984 1 27 71 0 0 1 0 0 3038868 50956 444720 0 0 0 0 33100 1319126 2 27 71 0 0 1 0 0 3038868 50956 444720 0 0 0 0 33097 1317968 1 27 72 0 0 2 0 0 3038868 50964 444720 0 0 0 1 33104 1318558 2 27 71 0 0 We can switch faster with NO_TTWU_QUEUE, so we switch more, and that hurts netperf UDP_STREAM throughput.. somehow. Fatter is better is not the way context switch happy benchmarks usually work. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/