From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935240AbcA1NuS (ORCPT ); Thu, 28 Jan 2016 08:50:18 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:43103 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934945AbcA1NuN (ORCPT ); Thu, 28 Jan 2016 08:50:13 -0500 Subject: Re: [PATCH] printk, allow different timestamps for printk.time [v2] To: Prarit Bhargava , linux-kernel@vger.kernel.org References: <1453985029-25912-1-git-send-email-prarit@redhat.com> <56AA0F16.1020806@virtuozzo.com> <56AA14F6.7060802@redhat.com> Cc: John Stultz , Xunlei Pang , Thomas Gleixner , Baolin Wang , Andrew Morton , Greg Kroah-Hartman , Petr Mladek , Tejun Heo , Peter Hurley , Joe Perches From: Vasily Averin X-Enigmail-Draft-Status: N1110 Message-ID: <56AA1C7B.5030109@virtuozzo.com> Date: Thu, 28 Jan 2016 16:49:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <56AA14F6.7060802@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28.01.2016 16:17, Prarit Bhargava wrote: > On 01/28/2016 07:52 AM, Vasily Averin wrote: >> Dear Prarit, >> > > Hi Vasily, Thanks for your suggestions. > >> I have no objections about your patch, >> bit in fact I doubt we really need to convert each timestamp in kernel logs. >> How do you think is it probably better to convert only one timestamp per screen ? > > How do you measure a screen? :) I mean 80x25, but you're right, it makes sense to do it configurable. >> I.e. convert it in each 25th string only? > > While your suggestion does work for a flood of messages this will miss > situations where an event occurred hours/minutes/seconds earlier leading to a > panic. > >> Or just do it once per N seconds? > > I've tried several other versions of the patch and other userspace options (such > as "date +%N > /tmp/kmsg" every second, setting up a timer to dump the real > time, etc.). Assuming that the disks didn't die (which was also part of the > problem I have seen) the printk buffer is finite in size and it is easy to fill > the buffer if you're not careful. > >> And do not replace original timestamp but add converted one? > > I'm not sure I see the benefit of having two timestamps but if someone really > wanted that I could add an additional patch to do it. I investigate periodically various "node hangs" issues, without saved vmcore, /var/log/messages, net or serial console. All what I have is screenshot on local console, in worst case 80x25. I'm ready to lose ~10 characters on each string for short timesetamp, and of course I would be happy to know real date of these messages. But for me it's enough to see full date once per screen, and have short relative timestamp on other strings. > At the end of the day I need to be able to determine in real time what happened > on a system and to make that as easy as possible for a human to read. > > P. >