Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933853Ab3CSWiy (ORCPT ); Tue, 19 Mar 2013 18:38:54 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:47100 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933625Ab3CSWiw (ORCPT ); Tue, 19 Mar 2013 18:38:52 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: HATAYAMA Daisuke Cc: vgoyal@redhat.com, cpw@sgi.com, kumagai-atsushi@mxc.nes.nec.co.jp, lisa.mitchell@hp.com, heiko.carstens@de.ibm.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, zhangyanfei@cn.fujitsu.com References: <20130316040003.15064.62308.stgit@localhost6.localdomain6> <20130316040228.15064.28019.stgit@localhost6.localdomain6> Date: Tue, 19 Mar 2013 15:38:45 -0700 In-Reply-To: <20130316040228.15064.28019.stgit@localhost6.localdomain6> (HATAYAMA Daisuke's message of "Sat, 16 Mar 2013 13:02:29 +0900") Message-ID: <877gl3koay.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX1+BUDxuLUuV2ATjnbIUnIv+5+fDDO0Am2M= X-SA-Exim-Connect-IP: 98.207.154.105 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.1 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_04 7+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_02 5+ unique symbols in subject X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;HATAYAMA Daisuke X-Spam-Relay-Country: Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1196 Lines: 27 HATAYAMA Daisuke writes: > If there's some vmcore object that doesn't satisfy page-size boundary > requirement, remap_pfn_range() fails to remap it to user-space. > > Objects that posisbly don't satisfy the requirement are ELF note > segments only. The memory chunks corresponding to PT_LOAD entries are > guaranteed to satisfy page-size boundary requirement by the copy from > old memory to buffer in 2nd kernel done in later patch. > > This patch doesn't copy each note segment into the 2nd kernel since > they amount to so large in total if there are multiple CPUs. For > example, current maximum number of CPUs in x86_64 is 5120, where note > segments exceed 1MB with NT_PRSTATUS only. So you require the first kernel to reserve an additional 20MB, instead of just 1.6MB. 336 bytes versus 4096 bytes. That seems like completely the wrong tradeoff in memory consumption, filesize, and backwards compatibility. Eric -- 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/