From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 6AD2E6B0031 for ; Tue, 18 Feb 2014 07:40:30 -0500 (EST) Received: by mail-pd0-f171.google.com with SMTP id g10so16196169pdj.2 for ; Tue, 18 Feb 2014 04:40:30 -0800 (PST) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [119.145.14.64]) by mx.google.com with ESMTPS id s4si18230764pbg.3.2014.02.18.04.40.26 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 18 Feb 2014 04:40:28 -0800 (PST) Message-ID: <53035433.3000405@huawei.com> Date: Tue, 18 Feb 2014 20:38:11 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [PATCH V2] mm: add a new command-line kmemcheck value References: <53017544.90908@huawei.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vegard Nossum Cc: Ingo Molnar , "H. Peter Anvin" , Vegard Nossum , Pekka Enberg , Mel Gorman , the arch/x86 maintainers , LKML , Linux MM , Li Zefan On 2014/2/18 18:28, Vegard Nossum wrote: > On 17 February 2014 03:34, Xishi Qiu wrote: >> If we want to debug the kernel memory, we should turn on CONFIG_KMEMCHECK >> and rebuild the kernel. This always takes a long time and sometimes >> impossible, e.g. users don't have the kernel source code or the code >> is different from "www.kernel.org" (private features may be added to the >> kernel, and usually users can not get the whole code). >> >> This patch adds a new command-line "kmemcheck=3", then the kernel will run >> as the same as CONFIG_KMEMCHECK=off even CONFIG_KMEMCHECK is turn on. >> "kmemcheck=0/1/2" is the same as originally. This means we can always turn >> on CONFIG_KMEMCHECK, and use "kmemcheck=3" to control it on/off with out >> rebuild the kernel. >> >> In another word, "kmemcheck=3" is equivalent: >> 1) turn off CONFIG_KMEMCHECK >> 2) rebuild the kernel >> 3) reboot >> >> The different between kmemcheck=0 and 3 is the used memory and nr_cpus. >> Also kmemcheck=0 can used in runtime, and kmemcheck=3 is only used in boot. >> boottime: kmemcheck=0/1/2/3 (command-line) >> runtime: kmemcheck=0/1/2 (/proc/sys/kernel/kmemcheck) > > This is not the right way to do what you want. > > The behaviour that we want is: > > - CONFIG_KMEMCHECK=y + kmemcheck=0 (boot parameter) should have a > minimal runtime impact and not limit the number of CPUs > - CONFIG_KMEMCHECK=y + kmemcheck=1 should limit the number of CPUs during boot > - setting kmemcheck to 1 via /proc/sys/kernel/kmemcheck should > probably return an error if more than 1 CPU is online > > > Vegard > Hi Vegard, Thank you for your reply. If we only use "kmemcheck=0" to control, how about the used memory? Will it use about twice as much memory as normal? Thanks, Xishi Qiu > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org