Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932169AbZKLEd6 (ORCPT ); Wed, 11 Nov 2009 23:33:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760073AbZKLEd5 (ORCPT ); Wed, 11 Nov 2009 23:33:57 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:40198 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760070AbZKLEd5 (ORCPT ); Wed, 11 Nov 2009 23:33:57 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Message-ID: <4AFB9029.9000208@jp.fujitsu.com> Date: Thu, 12 Nov 2009 13:33:45 +0900 From: Hidetoshi Seto User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: Stanislaw Gruszka CC: =?UTF-8?B?QW3DqXJpY28gV2FuZw==?= , Peter Zijlstra , Spencer Candland , linux-kernel@vger.kernel.org, Ingo Molnar , Oleg Nesterov Subject: [PATCH] fix granularity of task_u/stime(), v2 References: <4AF0C97F.7000603@bluehost.com> <4AF123F5.50407@jp.fujitsu.com> <4AF26176.4080307@jp.fujitsu.com> <1257778154.4108.341.camel@laptop> <4AF8FD3C.2090008@jp.fujitsu.com> <4AF8FE76.406@jp.fujitsu.com> <20091111121150.GA2549@dhcp-lab-161.englab.brq.redhat.com> <4AFB5019.7030901@jp.fujitsu.com> <4AFB77C2.8080705@jp.fujitsu.com> <2375c9f90911111855w20491a1er8d3400cf4e027855@mail.gmail.com> <4AFB8C21.6080404@jp.fujitsu.com> In-Reply-To: <4AFB8C21.6080404@jp.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2747 Lines: 94 Originally task_s/utime() were designed to return clock_t but later changed to return cputime_t by following commit: commit efe567fc8281661524ffa75477a7c4ca9b466c63 Author: Christian Borntraeger Date: Thu Aug 23 15:18:02 2007 +0200 It only changed the type of return value, but not the implementation. As the result the granularity of task_s/utime() is still that of clock_t, not that of cputime_t. So using task_s/utime() in __exit_signal() makes values accumulated to the signal struct to be rounded and coarse grained. This patch removes casts to clock_t in task_u/stime(), to keep granularity of cputime_t over the calculation. v2: Use div_u64() to avoid error "undefined reference to `__udivdi3`" on some 32bit systems. Signed-off-by: Hidetoshi Seto --- kernel/sched.c | 22 +++++++++++++--------- 1 files changed, 13 insertions(+), 9 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 3c11ae0..1f8d028 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5172,41 +5172,45 @@ cputime_t task_stime(struct task_struct *p) return p->stime; } #else + +#ifndef nsecs_to_cputime +# define nsecs_to_cputime(__nsecs) \ + msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC)) +#endif + 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); + cputime_t utime = p->utime, total = utime + p->stime; u64 temp; /* * Use CFS's precise accounting: */ - temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime); + temp = (u64)nsecs_to_cputime(p->se.sum_exec_runtime); if (total) { temp *= utime; do_div(temp, total); } - utime = (clock_t)temp; + utime = (cputime_t)temp; - p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime)); + p->prev_utime = max(p->prev_utime, utime); return p->prev_utime; } cputime_t task_stime(struct task_struct *p) { - clock_t stime; + cputime_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)); + stime = nsecs_to_cputime(p->se.sum_exec_runtime) - task_utime(p); if (stime >= 0) - p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime)); + p->prev_stime = max(p->prev_stime, stime); return p->prev_stime; } -- 1.6.5.2 -- 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/