Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759325AbYH0Q6r (ORCPT ); Wed, 27 Aug 2008 12:58:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756144AbYH0Q6Y (ORCPT ); Wed, 27 Aug 2008 12:58:24 -0400 Received: from g1t0028.austin.hp.com ([15.216.28.35]:10154 "EHLO g1t0028.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758960AbYH0Q6W (ORCPT ); Wed, 27 Aug 2008 12:58:22 -0400 Message-ID: <48B58792.5080501@hp.com> Date: Wed, 27 Aug 2008 09:57:54 -0700 From: Rick Jones User-Agent: Mozilla/5.0 (X11; U; HP-UX 9000/785; en-US; rv:1.7.13) Gecko/20060601 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andi Kleen CC: Evgeniy Polyakov , Eric Dumazet , Denys Fedoryshchenko , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: loaded router, excessive getnstimeofday in oprofile References: <200808220457.40892.denys@visp.net.lb> <20080826201406.GA24827@2ka.mipt.ru> <48B46B48.7030609@cosmosbay.com> <20080826205158.GA15266@2ka.mipt.ru> <87vdxmr53f.fsf@basil.nowhere.org> <48B57BD3.5050206@hp.com> <20080827162735.GW26610@one.firstfloor.org> <48B58586.3080806@hp.com> <20080827165635.GY26610@one.firstfloor.org> In-Reply-To: <20080827165635.GY26610@one.firstfloor.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1311 Lines: 38 Andi Kleen wrote: > On Wed, Aug 27, 2008 at 09:49:10AM -0700, Rick Jones wrote: > >>Andi Kleen wrote: >> >>>>Those banks really want to crank down on latency - to the point they >>>>start disabling interrupt coalescing. I bet they'd toss anything out >>>>they could to shave another microsecond. >>> >>> >>>This change would actually likely lower their latency. >> >>I'm guessing you mean increase their latency? I agree, it could - >>depends entirely on the PPS in production I suspect. > > > No, moving the time stamps into the socket decreases latency > for all packets that don't need time stamps. And they likely > have some packets which don't need time stamps too. Ah, since that part of the discussion wasn't in the quoted text I assumed you were talking about the disabling of interrupt coalescing. rick jones > > As a secondary effect if they use a RT kernel it might > be also beneficial to do the (depending on the platform) > costly time stamp in the lower priority socket context > than in the high priority interrupt thread. > > -Andi -- 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/