Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753819AbYANT00 (ORCPT ); Mon, 14 Jan 2008 14:26:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751379AbYANT0P (ORCPT ); Mon, 14 Jan 2008 14:26:15 -0500 Received: from zcars04f.nortel.com ([47.129.242.57]:47190 "EHLO zcars04f.nortel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751390AbYANT0O (ORCPT ); Mon, 14 Jan 2008 14:26:14 -0500 Message-ID: <478BB722.1020004@nortel.com> Date: Mon, 14 Jan 2008 13:25:22 -0600 From: "Chris Friesen" User-Agent: Mozilla Thunderbird 1.0.2-6 (X11/20050513) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Eric Dumazet CC: Ray Lee , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: questions on NAPI processing latency and dropped network packets References: <478654C3.60806@nortel.com> <2c0942db0801112137k3f3f885ek212d5cbaecb7fea0@mail.gmail.com> <478B8473.6080506@nortel.com> <478B943C.7080009@cosmosbay.com> In-Reply-To: <478B943C.7080009@cosmosbay.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 14 Jan 2008 19:25:29.0317 (UTC) FILETIME=[38F47950:01C856E3] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2541 Lines: 56 Eric Dumazet wrote: > Chris Friesen a écrit : >> Based on profiling and instrumentation it seems like the cost of >> sctp_endpoint_lookup_assoc() more than triples, which means that the >> amount of time that bottom halves are disabled in that function also >> triples. > > Any idea of the size of sctp hash size you have ? > (your dmesg probably includes a message starting with SCTP: Hash tables > configured... > How many concurrent sctp sockets are handled ? Our lab is currently rebooting, but I'll try and get this once it's back up. > Maybe sctp_assoc_hashfn() is too weak for your use, and some chains are > *really* long. Based on the profiling information we're spending time in sctp_endpoint_lookup_assoc() which doesn't actually use hashes, so I can't see how the hash would be related. I'm pretty new to SCTP though, so I may be missing something. Here's the top results from readprofile, unfortunately these are aggregated across both cpus so they don't really show what's going on. The key thing is that sctp_endpoint_lookup_assoc() is the most expensive kernel routine on this entire system. 3147 .power4_idle 22.4786 1712 .native_idle 20.3810 1234 .sctp_endpoint_lookup_assoc 2.1725 1212 ._spin_unlock_irqrestore 6.4468 778 .do_futex 0.3791 447 ._spin_unlock_irq 4.2981 313 .fget 1.7784 277 .fput 3.8472 275 .kfree 0.7473 234 .__kmalloc 0.5571 131 SystemCall_common 0.3411 130 .sctp_assoc_is_match 0.6373 123 .lock_sock 0.4155 119 .find_vma 0.6919 116 .kmem_cache_alloc 0.3580 111 .kmem_cache_free 0.3343 106 .skb_release_data 0.4907 102 .__copy_tofrom_user 0.0724 100 .exit_elf_binfmt 1.9231 100 .do_select 0.0820 Chris -- 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/