From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752615Ab0IOEqm (ORCPT ); Wed, 15 Sep 2010 00:46:42 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:41074 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752095Ab0IOEql (ORCPT ); Wed, 15 Sep 2010 00:46:41 -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: <201009151007.43232.knikanth@suse.de> References: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> <201009151007.43232.knikanth@suse.de> Message-Id: <20100915134347.C9EB.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 13:46:36 +0900 (JST) 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:". Here is the code. I think the page will become dirty, again. -------------------------------------------------------------- int try_to_free_swap(struct page *page) { VM_BUG_ON(!PageLocked(page)); if (!PageSwapCache(page)) return 0; if (PageWriteback(page)) return 0; if (page_swapcount(page)) return 0; delete_from_swap_cache(page); SetPageDirty(page); return 1; } From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 94A106B007B for ; Wed, 15 Sep 2010 00:46:45 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o8F4kfZt022619 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 15 Sep 2010 13:46:42 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 9CDEE45DE62 for ; Wed, 15 Sep 2010 13:46:38 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 6E90445DE55 for ; Wed, 15 Sep 2010 13:46:38 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 51F331DB803B for ; Wed, 15 Sep 2010 13:46:38 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id F3A4DE08001 for ; Wed, 15 Sep 2010 13:46:37 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH] After swapout/swapin private dirty mappings become clean In-Reply-To: <201009151007.43232.knikanth@suse.de> References: <20100915092239.C9D9.A69D9226@jp.fujitsu.com> <201009151007.43232.knikanth@suse.de> Message-Id: <20100915134347.C9EB.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 15 Sep 2010 13:46:36 +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: > 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:". Here is the code. I think the page will become dirty, again. -------------------------------------------------------------- int try_to_free_swap(struct page *page) { VM_BUG_ON(!PageLocked(page)); if (!PageSwapCache(page)) return 0; if (PageWriteback(page)) return 0; if (page_swapcount(page)) return 0; delete_from_swap_cache(page); SetPageDirty(page); return 1; } -- 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