From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754454Ab3GJOeI (ORCPT ); Wed, 10 Jul 2013 10:34:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22221 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754084Ab3GJOeG (ORCPT ); Wed, 10 Jul 2013 10:34:06 -0400 Date: Wed, 10 Jul 2013 10:33:09 -0400 From: Vivek Goyal To: HATAYAMA Daisuke Cc: Michael Holzheu , Martin Schwidefsky , kexec@lists.infradead.org, Heiko Carstens , Jan Willeke , linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range() Message-ID: <20130710143309.GD5819@redhat.com> References: <1372707159-10425-1-git-send-email-holzheu@linux.vnet.ibm.com> <1372707159-10425-4-git-send-email-holzheu@linux.vnet.ibm.com> <51DA4ED9.60903@jp.fujitsu.com> <20130708112839.498ccfc6@holzheu> <20130708142826.GA9094@redhat.com> <51DBA47C.8090708@jp.fujitsu.com> <20130710104252.479a0f92@holzheu> <51DD2E5A.1030200@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51DD2E5A.1030200@jp.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 10, 2013 at 06:50:18PM +0900, HATAYAMA Daisuke wrote: [..] > If you want to avoid looking up vmcore_list that takes linear time w.r.t. the number > of the elements, you can still calculate the range of offsets in /proc/vmcore > corresponding to HSA during /proc/vmcore initialization. > > Also, could you tell me how often and how much the HSA region is during crash dumping? > I guess the read to HSA is done mainly during early part of crash dumping process only. > According to the code, it appears at most 64MiB only. Then, I feel performance is not > a big issue. > > Also, cost of WARN_ONCE() is one memory access only in the 2nd and later calls. I don't > think it too much overhead... Hi Hatayama, I think michael's proposal of just putting in WARN_ONCE for non s390 arch sounds reasonable. It is simple and meets your need of being able to detect that non s390 arch don't make use of mmap() path yet. Introducing in_valid_fault_range() kind of sounds overkill to me for this issue. Thanks Vivek From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UwvSz-0006Ny-LP for kexec@lists.infradead.org; Wed, 10 Jul 2013 14:34:02 +0000 Date: Wed, 10 Jul 2013 10:33:09 -0400 From: Vivek Goyal Subject: Re: [PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range() Message-ID: <20130710143309.GD5819@redhat.com> References: <1372707159-10425-1-git-send-email-holzheu@linux.vnet.ibm.com> <1372707159-10425-4-git-send-email-holzheu@linux.vnet.ibm.com> <51DA4ED9.60903@jp.fujitsu.com> <20130708112839.498ccfc6@holzheu> <20130708142826.GA9094@redhat.com> <51DBA47C.8090708@jp.fujitsu.com> <20130710104252.479a0f92@holzheu> <51DD2E5A.1030200@jp.fujitsu.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <51DD2E5A.1030200@jp.fujitsu.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: HATAYAMA Daisuke Cc: kexec@lists.infradead.org, Heiko Carstens , Jan Willeke , linux-kernel@vger.kernel.org, Martin Schwidefsky , Michael Holzheu On Wed, Jul 10, 2013 at 06:50:18PM +0900, HATAYAMA Daisuke wrote: [..] > If you want to avoid looking up vmcore_list that takes linear time w.r.t. the number > of the elements, you can still calculate the range of offsets in /proc/vmcore > corresponding to HSA during /proc/vmcore initialization. > > Also, could you tell me how often and how much the HSA region is during crash dumping? > I guess the read to HSA is done mainly during early part of crash dumping process only. > According to the code, it appears at most 64MiB only. Then, I feel performance is not > a big issue. > > Also, cost of WARN_ONCE() is one memory access only in the 2nd and later calls. I don't > think it too much overhead... Hi Hatayama, I think michael's proposal of just putting in WARN_ONCE for non s390 arch sounds reasonable. It is simple and meets your need of being able to detect that non s390 arch don't make use of mmap() path yet. Introducing in_valid_fault_range() kind of sounds overkill to me for this issue. Thanks Vivek _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec