From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753123AbbE0O4a (ORCPT ); Wed, 27 May 2015 10:56:30 -0400 Received: from mail-ie0-f170.google.com ([209.85.223.170]:33246 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751602AbbE0O42 (ORCPT ); Wed, 27 May 2015 10:56:28 -0400 Message-ID: <1432738585.4060.392.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [PATCH] net: tcp: Fix a PTO timing granularity issue From: Eric Dumazet To: Ido Yariv Cc: David Laight , "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy , Nandita Dukkipati , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Ido Yariv Date: Wed, 27 May 2015 07:56:25 -0700 In-Reply-To: <20150527144029.GA558@WorkStation.home> References: <1432663992.4060.286.camel@edumazet-glaptop2.roam.corp.google.com> <1432671437-19140-1-git-send-email-ido@wizery.com> <063D6719AE5E284EB5DD2968C1650D6D1CB40A1A@AcuExch.aculab.com> <1432734077.4060.382.camel@edumazet-glaptop2.roam.corp.google.com> <20150527144029.GA558@WorkStation.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2015-05-27 at 10:40 -0400, Ido Yariv wrote: > HZ=100 is used on some embedded platforms, so it's still something we > have to deal with unfortunately.. > > Since the '2' here is a lower bound, and msecs_to_jiffies(10) will > return values greater than 2 for HZ>100 anyway, always ensuring the > 2 jiffies lower bound shouldn't impact the behavior when HZ=1000. > > However, as far as I can tell, comparing msecs_to_jiffies(10) to 2, or > comparing the whole timeout to 2 doesn't make much difference, since > msecs_to_jiffies isn't inlined. > > In other words, keeping the #if shouldn't make much difference in behavior, > but will save the small comparison. Yes, I guess David point is to have a macro in include/linux/tcp.h so that we can have a nice comment, and not having #if ... in a C file. Maybe other timers in TCP need the same care (I am not asking you to find them, but having a macro would ease things perhaps)