From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752827Ab0IOAYr (ORCPT ); Tue, 14 Sep 2010 20:24:47 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:34002 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751819Ab0IOAYq (ORCPT ); Tue, 14 Sep 2010 20:24:46 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Nikanth Karthikesan Subject: Re: [PATCH] After swapout/swapin private dirty mappings become clean Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Matt Mackall , balbir@linux.vnet.ibm.com, rguenther@novell.com, matz@novell.com In-Reply-To: <201009141640.55650.knikanth@suse.de> References: <201009141640.55650.knikanth@suse.de> Message-Id: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Wed, 15 Sep 2010 09:24:31 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > /proc/$pid/smaps broken: After swapout/swapin private dirty mappings become > clean. > > When a page with private file mapping becomes dirty, the vma will be in both > i_mmap tree and anon_vma list. The /proc/$pid/smaps will account these pages > as dirty and backed by the file. > > But when those dirty pages gets swapped out, and when they are read back from > swap, they would be marked as clean, as it should be, as they are part of swap > cache now. > > But the /proc/$pid/smaps would report the vma as a mapping of a file and it is > clean. The pages are actually in same state i.e., dirty with respect to file > still, but which was once reported as dirty is now being reported as clean to > user-space. > > This confuses tools like gdb which uses this information. Those tools think > that those pages were never modified and it creates problem when they create > dumps. > > The file mapping of the vma also cannot be broken as pages never read earlier, > will still have to come from the file. Just that those dirty pages have become > clean anonymous pages. > > During swaping in, restoring the exact state as dirty file-backed pages before > swapout would be useless, as there in no real bug. Breaking the vma with only > anonymous pages as seperate vmas unnecessary may not be a good thing as well. > So let us just export the information that a file-backed vma has anonymous > dirty pages. Why can't gdb check Swap: field in smaps? I think Swap!=0 mean we need dump out. Am I missing anything? - kosaki > > Export this information in smaps by prepending file-names with "[anon]+", when > some of the pages in a file backed vma become anonymous. > > Signed-off-by: Nikanth Karthikesan > > --- > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 439fc1f..68f9806 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -242,6 +242,8 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) > */ > if (file) { > pad_len_spaces(m, len); > + if (vma->anon_vma) > + seq_puts(m, "[anon]+"); > seq_path(m, &file->f_path, "\n"); > } else { > const char *name = arch_vma_name(vma); > > > -- > 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 > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 96BD56B0047 for ; Tue, 14 Sep 2010 20:24:47 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o8F0OiJD015995 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 15 Sep 2010 09:24:44 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 2347C45DE4F for ; Wed, 15 Sep 2010 09:24:44 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id EDCE445DE4E for ; Wed, 15 Sep 2010 09:24:43 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id D6B3E1DB803B for ; Wed, 15 Sep 2010 09:24:43 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 912C81DB8038 for ; Wed, 15 Sep 2010 09:24:43 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH] After swapout/swapin private dirty mappings become clean In-Reply-To: <201009141640.55650.knikanth@suse.de> References: <201009141640.55650.knikanth@suse.de> Message-Id: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 15 Sep 2010 09:24:31 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Nikanth Karthikesan Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Matt Mackall , balbir@linux.vnet.ibm.com, rguenther@novell.com, matz@novell.com List-ID: > /proc/$pid/smaps broken: After swapout/swapin private dirty mappings become > clean. > > When a page with private file mapping becomes dirty, the vma will be in both > i_mmap tree and anon_vma list. The /proc/$pid/smaps will account these pages > as dirty and backed by the file. > > But when those dirty pages gets swapped out, and when they are read back from > swap, they would be marked as clean, as it should be, as they are part of swap > cache now. > > But the /proc/$pid/smaps would report the vma as a mapping of a file and it is > clean. The pages are actually in same state i.e., dirty with respect to file > still, but which was once reported as dirty is now being reported as clean to > user-space. > > This confuses tools like gdb which uses this information. Those tools think > that those pages were never modified and it creates problem when they create > dumps. > > The file mapping of the vma also cannot be broken as pages never read earlier, > will still have to come from the file. Just that those dirty pages have become > clean anonymous pages. > > During swaping in, restoring the exact state as dirty file-backed pages before > swapout would be useless, as there in no real bug. Breaking the vma with only > anonymous pages as seperate vmas unnecessary may not be a good thing as well. > So let us just export the information that a file-backed vma has anonymous > dirty pages. Why can't gdb check Swap: field in smaps? I think Swap!=0 mean we need dump out. Am I missing anything? - kosaki > > Export this information in smaps by prepending file-names with "[anon]+", when > some of the pages in a file backed vma become anonymous. > > Signed-off-by: Nikanth Karthikesan > > --- > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 439fc1f..68f9806 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -242,6 +242,8 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) > */ > if (file) { > pad_len_spaces(m, len); > + if (vma->anon_vma) > + seq_puts(m, "[anon]+"); > seq_path(m, &file->f_path, "\n"); > } else { > const char *name = arch_vma_name(vma); > > > -- > 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 > -- 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