Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752026AbWJaDDJ (ORCPT ); Mon, 30 Oct 2006 22:03:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752028AbWJaDDJ (ORCPT ); Mon, 30 Oct 2006 22:03:09 -0500 Received: from mta2.srv.hcvlny.cv.net ([167.206.4.197]:3522 "EHLO mta2.srv.hcvlny.cv.net") by vger.kernel.org with ESMTP id S1752026AbWJaDDI (ORCPT ); Mon, 30 Oct 2006 22:03:08 -0500 Date: Mon, 30 Oct 2006 22:03:03 -0500 From: Shailabh Nagar Subject: Re: [PATCH] taskstats: fix sub-threads accounting In-reply-to: <20061030213749.GA3035@oleg> To: Oleg Nesterov Cc: Andrew Morton , Balbir Singh , Jay Lan , linux-kernel@vger.kernel.org Message-id: <4546BCE7.6020800@watson.ibm.com> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT References: <20061030213749.GA3035@oleg> User-Agent: Thunderbird 1.5.0.7 (Windows/20060909) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2554 Lines: 81 Oleg Nesterov wrote: > If there are no listeners, taskstats_exit_send() just returns because > taskstats_exit_alloc() didn't allocate *tidstats. This is wrong, each > sub-thread should do fill_tgid_exit() on exit, otherwise its ->delays > is not recorded in ->signal->stats and lost. Good catch. Thanks for the detailed look at the delay accounting code. > > Q: We don't send TASKSTATS_TYPE_AGGR_TGID when single-threaded process > exits. Is it good? How can the listener figure out that it was actually > a process exit, not sub-thread? We had a detailed discussion on this on lkml earlier. The overhead of sending essentially the same data twice (once as AGGR_TGID and once as PID) was deemed too heavy esp. as the taskstats structure size grew. Also, single threaded exit is a common case. Using process events, its possible for user space to distinguish single threaded process exits. > > Signed-off-by: Oleg Nesterov Acked-by: Shailabh Nagar > > --- STATS/kernel/taskstats.c~2_send 2006-10-30 23:47:46.000000000 +0300 > +++ STATS/kernel/taskstats.c 2006-10-31 00:14:42.000000000 +0300 > @@ -446,10 +446,9 @@ void taskstats_exit_send(struct task_str > int is_thread_group; > struct nlattr *na; > > - if (!family_registered || !tidstats) > + if (!family_registered) > return; > > - rc = 0; > /* > * Size includes space for nested attributes > */ > @@ -457,8 +456,15 @@ void taskstats_exit_send(struct task_str > nla_total_size(sizeof(struct taskstats)) + nla_total_size(0); > > is_thread_group = (tsk->signal->stats != NULL); > - if (is_thread_group) > - size = 2 * size; /* PID + STATS + TGID + STATS */ > + if (is_thread_group) { > + /* PID + STATS + TGID + STATS */ > + size = 2 * size; > + /* fill the tsk->signal->stats structure */ > + fill_tgid_exit(tsk); > + } > + > + if (!tidstats) > + return; > > rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size); > if (rc < 0) > @@ -478,11 +484,8 @@ void taskstats_exit_send(struct task_str > goto send; > > /* > - * tsk has/had a thread group so fill the tsk->signal->stats structure > * Doesn't matter if tsk is the leader or the last group member leaving > */ > - > - fill_tgid_exit(tsk); > if (!group_dead) > goto send; > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/