From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from terminus.zytor.com ([2001:1868:205::10] helo=mail.zytor.com) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Ud8CK-0003VX-MB for kexec@lists.infradead.org; Fri, 17 May 2013 00:07:01 +0000 Message-ID: <51957469.2000008@zytor.com> Date: Thu, 16 May 2013 17:06:01 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH v6 0/8] kdump, vmcore: support mmap() on /proc/vmcore References: <20130515090507.28109.28956.stgit@localhost6.localdomain6> In-Reply-To: <20130515090507.28109.28956.stgit@localhost6.localdomain6> 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: riel@redhat.com, hughd@google.com, jingbai.ma@hp.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, lisa.mitchell@hp.com, linux-mm@kvack.org, kumagai-atsushi@mxc.nes.nec.co.jp, ebiederm@xmission.com, kosaki.motohiro@jp.fujitsu.com, zhangyanfei@cn.fujitsu.com, akpm@linux-foundation.org, walken@google.com, cpw@sgi.com, vgoyal@redhat.com On 05/15/2013 02:05 AM, HATAYAMA Daisuke wrote: > Currently, read to /proc/vmcore is done by read_oldmem() that uses > ioremap/iounmap per a single page. For example, if memory is 1GB, > ioremap/iounmap is called (1GB / 4KB)-times, that is, 262144 > times. This causes big performance degradation. read_oldmem() is fundamentally broken and unsafe. It needs to be unified with the plain /dev/mem code and any missing functionality fixed instead of "let's just do a whole new driver". -hpa _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec