From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752234Ab0IOEfD (ORCPT ); Wed, 15 Sep 2010 00:35:03 -0400 Received: from cantor.suse.de ([195.135.220.2]:35809 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752028Ab0IOEfB (ORCPT ); Wed, 15 Sep 2010 00:35:01 -0400 From: Nikanth Karthikesan Organization: suse.de To: KOSAKI Motohiro Subject: Re: [PATCH] After swapout/swapin private dirty mappings become clean Date: Wed, 15 Sep 2010 10:07:42 +0530 User-Agent: KMail/1.12.4 (Linux/2.6.31.12-0.2-default; KDE/4.3.5; x86_64; ; ) Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Matt Mackall , balbir@linux.vnet.ibm.com, rguenther@novell.com, matz@novell.com References: <201009141640.55650.knikanth@suse.de> <20100915092239.C9D9.A69D9226@jp.fujitsu.com> In-Reply-To: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201009151007.43232.knikanth@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 15 September 2010 05:54:31 KOSAKI Motohiro wrote: > > /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. > Yes. When the page is swapped out it is accounted in "Swap:". > Am I missing anything? > But when it gets swapped in back to memory, it is removed from "Swap:" and added to "Private_Clean:" instead of "Private_Dirty:". Thanks Nikanth > - 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 mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 7445A6B007B for ; Wed, 15 Sep 2010 00:35:03 -0400 (EDT) From: Nikanth Karthikesan Subject: Re: [PATCH] After swapout/swapin private dirty mappings become clean Date: Wed, 15 Sep 2010 10:07:42 +0530 References: <201009141640.55650.knikanth@suse.de> <20100915092239.C9D9.A69D9226@jp.fujitsu.com> In-Reply-To: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201009151007.43232.knikanth@suse.de> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: 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: On Wednesday 15 September 2010 05:54:31 KOSAKI Motohiro wrote: > > /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. > Yes. When the page is swapped out it is accounted in "Swap:". > Am I missing anything? > But when it gets swapped in back to memory, it is removed from "Swap:" and added to "Private_Clean:" instead of "Private_Dirty:". Thanks Nikanth > - 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