From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752253Ab3ADFQ6 (ORCPT ); Fri, 4 Jan 2013 00:16:58 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:54670 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750727Ab3ADFQ4 (ORCPT ); Fri, 4 Jan 2013 00:16:56 -0500 X-AuditID: 9c930179-b7becae000000e51-e4-50e665c5a85e From: Namhyung Kim To: Eric Dumazet Cc: Andrew Morton , David Miller , netdev , "linux-kernel\@vger.kernel.org" , Tom Herbert Subject: Re: [PATCH net-next] softirq: reduce latencies References: <1357216132.21409.24107.camel@edumazet-glaptop> <20130103124608.136fd65b.akpm@linux-foundation.org> <1357252875.21409.26390.camel@edumazet-glaptop> Date: Fri, 04 Jan 2013 14:16:53 +0900 In-Reply-To: <1357252875.21409.26390.camel@edumazet-glaptop> (Eric Dumazet's message of "Thu, 03 Jan 2013 14:41:15 -0800") Message-ID: <87r4m1r0hm.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thu, 03 Jan 2013 14:41:15 -0800, Eric Dumazet wrote: > On Thu, 2013-01-03 at 12:46 -0800, Andrew Morton wrote: >> Can this change cause worsened latencies in some situations? Say there >> are a large number of short-running actions queued. Presently we'll >> dispatch ten of them and return. With this change we'll dispatch many >> more of them - however many consume 2ms. So worst-case latency >> increases from "10 * not-much" to "2 ms". > > I tried to reproduce such workload but couldnt. 2 ms (or more exactly 1 > to 2 ms given the jiffies/HZ granularity) is about the time needed to > process 1000 frames on current hardware. Probably a silly question: Why not using ktime rather than jiffies for this? Thanks, Namhyung