From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Multicast packet loss Date: Fri, 27 Feb 2009 21:12:06 +0100 Message-ID: <49A84916.9090106@cosmosbay.com> References: <49833DBC.7040607@athenacr.com> <20090130200330.GA12659@hmsreliant.think-freely.org> <49837F56.2020502@athenacr.com> <49838213.90700@cosmosbay.com> <49A8375A.6000006@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Kenny Chang , netdev@vger.kernel.org To: Christoph Lameter Return-path: Received: from gw1.cosmosbay.com ([212.99.114.194]:58756 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753963AbZB0UMr convert rfc822-to-8bit (ORCPT ); Fri, 27 Feb 2009 15:12:47 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Christoph Lameter a =E9crit : > On Fri, 27 Feb 2009, Eric Dumazet wrote: >=20 >> Christoph Lameter a ?crit : >>> On Fri, 30 Jan 2009, Eric Dumazet wrote: >>>> 2.6.29-rc contains UDP receive improvements (lockless) >>>> Problem is multicast handling was not yet updated, but could be :) >>> When will that happen? >> When proven necessary :) >> >> Kenny problem is about scheduling storm. The extra spin_lock() in UD= P >> multicast receive is not a problem. >=20 > My tests here show that 2.6.29-rc5 still looses ~5usec vs. 2.6.22 via > UDP. This would fix a regression..... >=20 Could you elaborate ? I just retried Kenny test here. As one cpu is looping in ksoftirqd, onl= y this cpu touches the spin_lock, so spin_lock()/spin_unlock() is free. oprofile shows that udp stack is lightweight in this case. Problem is a= bout wakeing up so many threads... CPU: Core 2, speed 3000.16 MHz (estimated) Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a u= nit mask of 0x00 (Unhalted core cycles) count 100000 samples cum. samples % cum. % symbol name 356857 356857 15.1789 15.1789 schedule 274028 630885 11.6557 26.8346 mwait_idle 189218 820103 8.0484 34.8829 __skb_recv_datagram 116903 937006 4.9725 39.8554 skb_release_data 103152 1040158 4.3876 44.2430 lock_sock_nested 89600 1129758 3.8111 48.0541 udp_recvmsg 74171 1203929 3.1549 51.2089 copy_to_user 72299 1276228 3.0752 54.2842 set_next_entity 60392 1336620 2.5688 56.8529 sched_clock_cpu 54026 1390646 2.2980 59.1509 __slab_free 50212 1440858 2.1358 61.2867 prepare_to_wait_exclusive 38689 1479547 1.6456 62.9323 cpu_idle 38142 1517689 1.6224 64.5547 __switch_to 36701 1554390 1.5611 66.1157 hrtick_start_fair 36673 1591063 1.5599 67.6756 dst_release 36268 1627331 1.5427 69.2183 sys_recvfrom 35052 1662383 1.4909 70.7092 kmem_cache_free 32680 1695063 1.3900 72.0992 pick_next_task_fair 31209 1726272 1.3275 73.4267 try_to_wake_up 30382 1756654 1.2923 74.7190 dequeue_task_fair 29048 1785702 1.2356 75.9545 __copy_skb_header 28801 1814503 1.2250 77.1796 sock_def_readable 28655 1843158 1.2188 78.3984 enqueue_task_fair 27232 1870390 1.1583 79.5567 update_curr 21688 1892078 0.9225 80.4792 copy_from_user 18832 1910910 0.8010 81.2802 sysenter_past_esp 17732 1928642 0.7542 82.0345 finish_task_switch 17583 1946225 0.7479 82.7824 resched_task 17367 1963592 0.7387 83.5211 native_sched_clock 15691 1979283 0.6674 84.1885 task_rq_lock 15352 1994635 0.6530 84.8415 sock_queue_rcv_skb 15022 2009657 0.6390 85.4804 udp_queue_rcv_skb 13999 2023656 0.5954 86.0759 __update_sched_clock 12284 2035940 0.5225 86.5984 skb_copy_datagram_iovec 11869 2047809 0.5048 87.1032 release_sock 10986 2058795 0.4673 87.5705 __wake_up_sync 10488 2069283 0.4461 88.0166 sock_recvmsg 9686 2078969 0.4120 88.4286 skb_queue_tail 9425 2088394 0.4009 88.8295 sys_socketcall