From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932222Ab2DJAfz (ORCPT ); Mon, 9 Apr 2012 20:35:55 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:39947 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753320Ab2DJAfx (ORCPT ); Mon, 9 Apr 2012 20:35:53 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <4F837FE2.7010805@jp.fujitsu.com> Date: Tue, 10 Apr 2012 09:33:38 +0900 From: KAMEZAWA Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:11.0) Gecko/20120327 Thunderbird/11.0.1 MIME-Version: 1.0 To: Hugh Dickins CC: KOSAKI Motohiro , Konstantin Khlebnikov , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Markus Trippelsdorf Subject: Re: [PATCH] mm: sync rss-counters at the end of exit_mm() References: <20120409200336.8368.63793.stgit@zurg> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2012/04/10 7:03), Hugh Dickins wrote: > On Mon, 9 Apr 2012, KOSAKI Motohiro wrote: >> On Mon, Apr 9, 2012 at 4:03 PM, Konstantin Khlebnikov >> wrote: >>> On task's exit do_exit() calls sync_mm_rss() but this is not enough, >>> there can be page-faults after this point, for example exit_mm() -> >>> mm_release() -> put_user() (for processing tsk->clear_child_tid). >>> Thus there may be some rss-counters delta in current->rss_stat. >> >> Seems reasonable. > > Yes, I think Konstantin has probably caught it; > but I'd like to hear confirmation from Markus. > >> but I have another question. Do we have any reason to >> keep sync_mm_rss() in do_exit()? I havn't seen any reason that thread exiting >> makes rss consistency. > > IIRC it's all about the hiwater_rss/maxrss stuff: we want to sync the > maximum rss into mm->hiwater_rss before it's transferred to signal->maxrss, > and later made visible to the user though getrusage(RUSAGE_CHILDREN,) - > does your reading confirm that? > IIRC, sync_mm_rss() in do_exit() is for synchronizing rsscounter for taskacct. mm->maxrss is sent to listener by xacct_add_tsk(). It's needed to be synchronized before taskstat_exit().. Hm, but, exit_mm() is placed after taskstat_exit(). Thanks, -Kame From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 3B3866B004A for ; Mon, 9 Apr 2012 20:35:54 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 67B883EE0BD for ; Tue, 10 Apr 2012 09:35:52 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 4FE2045DEA6 for ; Tue, 10 Apr 2012 09:35:52 +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 3531E45DEB2 for ; Tue, 10 Apr 2012 09:35:52 +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 297F61DB8038 for ; Tue, 10 Apr 2012 09:35:52 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.240.81.133]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id D8C2D1DB8040 for ; Tue, 10 Apr 2012 09:35:51 +0900 (JST) Message-ID: <4F837FE2.7010805@jp.fujitsu.com> Date: Tue, 10 Apr 2012 09:33:38 +0900 From: KAMEZAWA Hiroyuki MIME-Version: 1.0 Subject: Re: [PATCH] mm: sync rss-counters at the end of exit_mm() References: <20120409200336.8368.63793.stgit@zurg> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: KOSAKI Motohiro , Konstantin Khlebnikov , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Markus Trippelsdorf (2012/04/10 7:03), Hugh Dickins wrote: > On Mon, 9 Apr 2012, KOSAKI Motohiro wrote: >> On Mon, Apr 9, 2012 at 4:03 PM, Konstantin Khlebnikov >> wrote: >>> On task's exit do_exit() calls sync_mm_rss() but this is not enough, >>> there can be page-faults after this point, for example exit_mm() -> >>> mm_release() -> put_user() (for processing tsk->clear_child_tid). >>> Thus there may be some rss-counters delta in current->rss_stat. >> >> Seems reasonable. > > Yes, I think Konstantin has probably caught it; > but I'd like to hear confirmation from Markus. > >> but I have another question. Do we have any reason to >> keep sync_mm_rss() in do_exit()? I havn't seen any reason that thread exiting >> makes rss consistency. > > IIRC it's all about the hiwater_rss/maxrss stuff: we want to sync the > maximum rss into mm->hiwater_rss before it's transferred to signal->maxrss, > and later made visible to the user though getrusage(RUSAGE_CHILDREN,) - > does your reading confirm that? > IIRC, sync_mm_rss() in do_exit() is for synchronizing rsscounter for taskacct. mm->maxrss is sent to listener by xacct_add_tsk(). It's needed to be synchronized before taskstat_exit().. Hm, but, exit_mm() is placed after taskstat_exit(). Thanks, -Kame -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org