Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161923AbdD0FYL (ORCPT ); Thu, 27 Apr 2017 01:24:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37444 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161899AbdD0FYA (ORCPT ); Thu, 27 Apr 2017 01:24:00 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6965946D084 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=xpang@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 6965946D084 Reply-To: xlpang@redhat.com Subject: Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section References: <1492688374-27903-1-git-send-email-xlpang@redhat.com> <20170426071916.GD5381@dhcp-128-65.nay.redhat.com> <59006DAB.8030908@redhat.com> <59007405.6070107@redhat.com> <20170427030607.GB10602@dhcp-128-65.nay.redhat.com> To: Dave Young , xlpang@redhat.com Cc: Juergen Gross , linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org, Baoquan He , Petr Tesarik , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman , Hari Bathini , akpm@linux-foundation.org, Michael Holzheu From: Xunlei Pang Message-ID: <590180AF.3030202@redhat.com> Date: Thu, 27 Apr 2017 13:25:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20170427030607.GB10602@dhcp-128-65.nay.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 27 Apr 2017 05:23:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1191 Lines: 28 On 04/27/2017 at 11:06 AM, Dave Young wrote: > [snip] >>>>> >>>>> static int __init crash_save_vmcoreinfo_init(void) >>>>> { >>>>> + /* One page should be enough for VMCOREINFO_BYTES under all archs */ >>>> Can we add a comment in the VMCOREINFO_BYTES header file about the one >>>> page assumption? >>>> >>>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096 >>> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE >>> definition which is exported to sysfs, also some platform has larger page size(64KB), so >>> I didn't touch this 4096 value. >>> >>> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3 >>> kimage_crash_copy_vmcoreinfo(). >> But on the other hand, using a separate page for them seems safer compared with >> using frequently-used slab, what's your opinion? > I feel current page based way is better. > > For 64k page the vmcore note size will increase it seems fine. Do you > have concern in mind? Since tools are supposed to acquire vmcoreinfo note size from sysfs, it should be safe to do so, except that there is some waste in memory for larger PAGE_SIZE. Regards, Xunlei