From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: 0% cpu usasge after fresh boot or net restart but 10% CPU if kernel flush route cache Date: Thu, 28 Jan 2010 22:16:27 +0100 Message-ID: <1264713387.3380.17.camel@edumazet-laptop> References: <41ac0f9e1001260858o7d2a6a6dgb37ecfba5c325932@mail.gmail.com> <1264605976.3197.8.camel@edumazet-laptop> <41ac0f9e1001271153u333a5e2aq6f473ccc6e6d1e23@mail.gmail.com> <1264627088.2892.7.camel@edumazet-laptop> <41ac0f9e1001280114x17951046oda3fddcae4b8b9d3@mail.gmail.com> <1264694957.2930.15.camel@edumazet-laptop> <41ac0f9e1001280826j1a4e6caar47ccfd357b6feb37@mail.gmail.com> <1264698380.2930.20.camel@edumazet-laptop> <41ac0f9e1001281049g119d5b1bgbc47f78150cac6ee@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org To: cold cold Return-path: Received: from mail-bw0-f227.google.com ([209.85.218.227]:45387 "EHLO mail-bw0-f227.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744Ab0A1VQb (ORCPT ); Thu, 28 Jan 2010 16:16:31 -0500 Received: by bwz27 with SMTP id 27so961457bwz.21 for ; Thu, 28 Jan 2010 13:16:29 -0800 (PST) In-Reply-To: <41ac0f9e1001281049g119d5b1bgbc47f78150cac6ee@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Le jeudi 28 janvier 2010 =C3=A0 20:49 +0200, cold cold a =C3=A9crit : > what you mean drop packets ? >=20 > i test 2 different things and shearing results with you > first test with high CPU is with garbage collection function > second results represent CPU usage with totally disabled garbage col= lection ell, you didnt describe your benchmark method. 1) your results were on different rx/tx workload, and describing your workload is very important to be able to compare results. Then it shoul= d be exactly same workload. =46or example, when tx/tx load is high enough, less cpu overhead is spe= nt on irq processing, since each IRQ delivers more packets per round. 2) you didnt sent "perf top" results for the second/last one. But the first "perf top" results showed less than 1% of cpu time was used by cache cleanup. I guess you dont want to focus on this, since its already very good. Usually, when we want to bench a router, we study how it deals with DDO= S workload. Feeding lot of packets to the device and study what percentag= e of them are actually transmitted. Goal being 100% of legit packets of course. Route cache settings matter in DDOS situations, and the flush operation can have a big impact on dropped frames because of cpu/ram congestion. Because of 600 seconds oscillations, its pretty hard to study exact cpu use of a router, unless taking samples on long periods.