From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754106AbYH3Pck (ORCPT ); Sat, 30 Aug 2008 11:32:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751960AbYH3Pcc (ORCPT ); Sat, 30 Aug 2008 11:32:32 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:53575 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751786AbYH3Pcb (ORCPT ); Sat, 30 Aug 2008 11:32:31 -0400 Subject: Re: Still seeing decreasing stime/utime From: Peter Zijlstra To: balbir@linux.vnet.ibm.com Cc: Spencer Candland , dmitry.adamushko@gmail.com, mingo@elte.hu, linux-kernel@vger.kernel.org In-Reply-To: <20080830135557.GA24039@balbir.in.ibm.com> References: <48B5C4C7.8040509@bluehost.com> <48B66BCC.8030207@linux.vnet.ibm.com> <48B702FA.8060308@bluehost.com> <20080828224502.GA1540@balbir.in.ibm.com> <48B859C8.5000001@bluehost.com> <48B8E102.5050503@linux.vnet.ibm.com> <1220095656.8426.23.camel@twins> <20080830135557.GA24039@balbir.in.ibm.com> Content-Type: text/plain Date: Sat, 30 Aug 2008 17:32:07 +0200 Message-Id: <1220110327.14894.40.camel@lappy.programming.kicks-ass.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2008-08-30 at 19:25 +0530, Balbir Singh wrote: > * Peter Zijlstra [2008-08-30 13:27:36]: > > > On Sat, 2008-08-30 at 11:26 +0530, Balbir Singh wrote: > > > Spencer Candland wrote: > > > >> Here is an experimental patch (I've just compiled and booted a machine > > > >> with it, I am unable to reproduce your problem), could you please test > > > >> it for me and see if it helps solve the problem > > > > > > > > Looks like this fixed it. I have been testing this for the last 16 > > > > hours and everything is looking good. > > > > > > > > > > Excellent! Ingo, Peter, do you like the patch? If so, could you please pick it > > > up Ingo. I think we should even push the fix to stable releases. > > > > Looks good, except for the issue you yourself earlier raised, a few of > > those functions looks too large to be inlined. > > > > Here's the updated revision with task_*time functions moved to sched.c > and inlining removed, except for task_gtime(). I've compiled and > booted a machine (x86_64) with this patch applied. > > Reported-by: spencer@bluehost.com > > Spencer reported a problem where utime and stime were going negative despite > the fixes in commit b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa. The suspected > reason for the problem is that signal_struct maintains it's own utime and > stime (of exited tasks), these are not updated using the new task_utime() > routine, hence sig->utime can go backwards and cause the same problem > to occur (sig->utime, adds tsk->utime and not task_utime()). This patch > fixes the problem > > TODO: using max(task->prev_utime, derived utime) works for now, but a more > generic solution is to implement cputime_max() and use the cputime_gt() > function for comparison. > > Comments? > > Signed-off-by: Balbir Singh Thanks Balbir! Acked-by: Peter Zijlstra > --- > > fs/proc/array.c | 59 -------------------------------------------------- > include/linux/sched.h | 4 +++ > kernel/exit.c | 6 ++--- > kernel/sched.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 66 insertions(+), 62 deletions(-) > > diff -puN kernel/exit.c~fix-utime-stime-moving-backwards kernel/exit.c > --- linux-2.6.27-rc3/kernel/exit.c~fix-utime-stime-moving-backwards 2008-08-29 03:14:57.000000000 +0530 > +++ linux-2.6.27-rc3-balbir/kernel/exit.c 2008-08-29 03:21:18.000000000 +0530 > @@ -115,9 +115,9 @@ static void __exit_signal(struct task_st > * We won't ever get here for the group leader, since it > * will have been the last reference on the signal_struct. > */ > - sig->utime = cputime_add(sig->utime, tsk->utime); > - sig->stime = cputime_add(sig->stime, tsk->stime); > - sig->gtime = cputime_add(sig->gtime, tsk->gtime); > + sig->utime = cputime_add(sig->utime, task_utime(tsk)); > + sig->stime = cputime_add(sig->stime, task_stime(tsk)); > + sig->gtime = cputime_add(sig->gtime, task_gtime(tsk)); > sig->min_flt += tsk->min_flt; > sig->maj_flt += tsk->maj_flt; > sig->nvcsw += tsk->nvcsw; > diff -puN fs/proc/array.c~fix-utime-stime-moving-backwards fs/proc/array.c > --- linux-2.6.27-rc3/fs/proc/array.c~fix-utime-stime-moving-backwards 2008-08-29 03:14:58.000000000 +0530 > +++ linux-2.6.27-rc3-balbir/fs/proc/array.c 2008-08-29 03:16:09.000000000 +0530 > @@ -349,65 +349,6 @@ int proc_pid_status(struct seq_file *m, > return 0; > } > > -/* > - * Use precise platform statistics if available: > - */ > -#ifdef CONFIG_VIRT_CPU_ACCOUNTING > -static cputime_t task_utime(struct task_struct *p) > -{ > - return p->utime; > -} > - > -static cputime_t task_stime(struct task_struct *p) > -{ > - return p->stime; > -} > -#else > -static cputime_t task_utime(struct task_struct *p) > -{ > - clock_t utime = cputime_to_clock_t(p->utime), > - total = utime + cputime_to_clock_t(p->stime); > - u64 temp; > - > - /* > - * Use CFS's precise accounting: > - */ > - temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime); > - > - if (total) { > - temp *= utime; > - do_div(temp, total); > - } > - utime = (clock_t)temp; > - > - p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime)); > - return p->prev_utime; > -} > - > -static cputime_t task_stime(struct task_struct *p) > -{ > - clock_t stime; > - > - /* > - * Use CFS's precise accounting. (we subtract utime from > - * the total, to make sure the total observed by userspace > - * grows monotonically - apps rely on that): > - */ > - stime = nsec_to_clock_t(p->se.sum_exec_runtime) - > - cputime_to_clock_t(task_utime(p)); > - > - if (stime >= 0) > - p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime)); > - > - return p->prev_stime; > -} > -#endif > - > -static cputime_t task_gtime(struct task_struct *p) > -{ > - return p->gtime; > -} > - > static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, > struct pid *pid, struct task_struct *task, int whole) > { > diff -puN include/linux/sched.h~fix-utime-stime-moving-backwards include/linux/sched.h > --- linux-2.6.27-rc3/include/linux/sched.h~fix-utime-stime-moving-backwards 2008-08-29 03:14:58.000000000 +0530 > +++ linux-2.6.27-rc3-balbir/include/linux/sched.h 2008-08-30 18:43:56.000000000 +0530 > @@ -1430,6 +1430,10 @@ static inline void put_task_struct(struc > __put_task_struct(t); > } > > +extern cputime_t task_utime(struct task_struct *p); > +extern cputime_t task_stime(struct task_struct *p); > +extern cputime_t task_gtime(struct task_struct *p); > + > /* > * Per process flags > */ > diff -puN kernel/sched.c~fix-utime-stime-moving-backwards kernel/sched.c > --- linux-2.6.27-rc3/kernel/sched.c~fix-utime-stime-moving-backwards 2008-08-30 18:38:15.000000000 +0530 > +++ linux-2.6.27-rc3-balbir/kernel/sched.c 2008-08-30 18:41:40.000000000 +0530 > @@ -4176,6 +4176,65 @@ void account_steal_time(struct task_stru > } > > /* > + * Use precise platform statistics if available: > + */ > +#ifdef CONFIG_VIRT_CPU_ACCOUNTING > +cputime_t task_utime(struct task_struct *p) > +{ > + return p->utime; > +} > + > +cputime_t task_stime(struct task_struct *p) > +{ > + return p->stime; > +} > +#else > +cputime_t task_utime(struct task_struct *p) > +{ > + clock_t utime = cputime_to_clock_t(p->utime), > + total = utime + cputime_to_clock_t(p->stime); > + u64 temp; > + > + /* > + * Use CFS's precise accounting: > + */ > + temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime); > + > + if (total) { > + temp *= utime; > + do_div(temp, total); > + } > + utime = (clock_t)temp; > + > + p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime)); > + return p->prev_utime; > +} > + > +cputime_t task_stime(struct task_struct *p) > +{ > + clock_t stime; > + > + /* > + * Use CFS's precise accounting. (we subtract utime from > + * the total, to make sure the total observed by userspace > + * grows monotonically - apps rely on that): > + */ > + stime = nsec_to_clock_t(p->se.sum_exec_runtime) - > + cputime_to_clock_t(task_utime(p)); > + > + if (stime >= 0) > + p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime)); > + > + return p->prev_stime; > +} > +#endif > + > +inline cputime_t task_gtime(struct task_struct *p) > +{ > + return p->gtime; > +} > + > +/* > * This function gets called by the timer code, with HZ frequency. > * We call it with interrupts disabled. > * > _ >