Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753934Ab2HCWZn (ORCPT ); Fri, 3 Aug 2012 18:25:43 -0400 Received: from na3sys009aog120.obsmtp.com ([74.125.149.140]:41027 "EHLO na3sys009aog120.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753604Ab2HCWZj (ORCPT ); Fri, 3 Aug 2012 18:25:39 -0400 MIME-Version: 1.0 In-Reply-To: <20120803221327.GA5102@kroah.com> References: <1344013004-32211-1-git-send-email-vikram.pandita@ti.com> <20120803200822.GC731@harshnoise.musicnaut.iki.fi> <20120803215954.GA4489@kroah.com> <20120803221327.GA5102@kroah.com> From: "Pandita, Vikram" Date: Fri, 3 Aug 2012 15:25:17 -0700 Message-ID: Subject: Re: [PATCH v3] printk: add option to print cpu id To: Greg KH Cc: Aaro Koskinen , Andi Kleen , kay@vrfy.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Mike Turquette , Vimarsh Zutshi Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2551 Lines: 63 On Fri, Aug 3, 2012 at 3:13 PM, Greg KH wrote: > On Fri, Aug 03, 2012 at 03:07:39PM -0700, Pandita, Vikram wrote: >> On Fri, Aug 3, 2012 at 2:59 PM, Greg KH wrote: >> > On Fri, Aug 03, 2012 at 02:24:20PM -0700, Pandita, Vikram wrote: >> >> Aaro >> >> >> >> On Fri, Aug 3, 2012 at 1:08 PM, Aaro Koskinen wrote: >> >> > Hi, >> >> > >> >> > On Fri, Aug 03, 2012 at 11:25:37AM -0700, Pandita, Vikram wrote: >> >> >> > And really: Wasting 1/3 of the 80 character line is too much. >> >> >> >> >> >> You _WASTE_ 4 chars only if you are interested in this info by >> >> >> enabling: CONFIG_PRINTK_CPUID >> >> > >> >> > I guess you waste 4 + 3 chars? You could optimize the length by checking >> >> > CONFIG_NR_CPUS? >> >> >> >> Good point. >> >> Looks there is a variable 'nr_cpu_ids' that could be used as well. >> >> >> >> If there is general consensus that the patch can help the arm >> >> community, and others in general, >> >> this optimization should be easy to implement - saving few chars space >> >> in each line of console output. >> >> >> >> For now i will stick to this v3 version of path, unless you think otherwise. >> > >> > I don't think is is something that anyone needs, and if you do, as >> > pointed out, you can use the trace function to make it happen. >> > >> >> This was something that got used internally and helped at times. > > Could you have used the trace point instead? As i understood the trace_prink(), one would need to modify existing printk -> trace_printk. Is my understanding correct? Most of the times the problem exhibits as a random hang, without having a clue which code to modify. That time one generic defconfig global switch is your first tool. Other issue i found, using this patch, that on multi-core ARM systems, almost 99% of times, IRQ's are handled by CPU0, even if CPU0 was really busy and other CPU's were free. I am yet to understand a good reason why. this patch also helped in other areas as mentioned in the thread http://marc.info/?l=linux-omap&m=134401269106619&w=2 Not sure how easy its to use trace_printk for such issues, i found having one defconfig option was much easier to get going. Correct me if i have not understood trace_printk well enough. > > greg k-h -- 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/