From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761601Ab3BNTte (ORCPT ); Thu, 14 Feb 2013 14:49:34 -0500 Received: from mail-pa0-f42.google.com ([209.85.220.42]:38358 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758666Ab3BNTtc (ORCPT ); Thu, 14 Feb 2013 14:49:32 -0500 From: Kevin Hilman To: Frederic Weisbecker Cc: Ingo Molnar , LKML , Andrew Morton , Li Zhong , Namhyung Kim , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Tony Luck , Fenghua Yu , Nicolas Pitre Subject: Re: [PATCH 2/8] cputime: Librarize per nsecs resolution cputime definitions References: <1359399845-10568-1-git-send-email-fweisbec@gmail.com> <1359399845-10568-3-git-send-email-fweisbec@gmail.com> Date: Thu, 14 Feb 2013 11:49:28 -0800 In-Reply-To: <1359399845-10568-3-git-send-email-fweisbec@gmail.com> (Frederic Weisbecker's message of "Mon, 28 Jan 2013 20:03:59 +0100") Message-ID: <87ehgid6bb.fsf@linaro.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Frederic Weisbecker writes: > The full dynticks cputime accounting that we'll soon introduce > will rely on sched_clock(). And its clock can have a per > nanosecond granularity. > > To prepare for this, we need to have a cputime_t implementation > that has this precision. > > ia64 virtual cputime accounting already uses that granularity > so all we need is to librarize its implementation in the asm > generic headers. ...except that for it to be truly generic (i.e. usable on 32-bit arches), it should be using do_div() for 64-bit divides. I understand this series is targetted at 64-bit platforms currently, but I'm looking (again) at getting adaptive NOHZ working on ARM, and this was the first obvious obstacle to even compiling. I see this is already merged into tip/sched/core, so below is a patch on top of that to convert to using do_div(). If you're OK with the approach, I'll post it formally to LKML. Thanks, Kevin >>From b1572b5ae67d4221277484e59d571b639775af70 Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Thu, 14 Feb 2013 11:27:36 -0800 Subject: [PATCH] cputime: use do_div() for nsec resolution conversion helpers For the nsec resolution conversions to be useful on non 64-bit architectures, do_div() needs to be used for the 64-bit divisions. Cc: Frederic Weisbecker Signed-off-by: Kevin Hilman --- include/asm-generic/cputime_nsecs.h | 51 +++++++++++++++++++++++++++---------- 1 file changed, 37 insertions(+), 14 deletions(-) diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h index b6485ca..daa6075 100644 --- a/include/asm-generic/cputime_nsecs.h +++ b/include/asm-generic/cputime_nsecs.h @@ -24,13 +24,17 @@ typedef u64 __nocast cputime64_t; /* * Convert cputime <-> jiffies (HZ) */ -#define cputime_to_jiffies(__ct) \ - ((__force u64)(__ct) / (NSEC_PER_SEC / HZ)) +static inline u64 cputime_to_jiffies(const cputime_t ct) +{ + cputime_t __ct = ct; + + do_div(__ct, NSEC_PER_SEC / HZ); + return __ct; +} #define cputime_to_scaled(__ct) (__ct) #define jiffies_to_cputime(__jif) \ (__force cputime_t)((__jif) * (NSEC_PER_SEC / HZ)) -#define cputime64_to_jiffies64(__ct) \ - ((__force u64)(__ct) / (NSEC_PER_SEC / HZ)) +#define cputime64_to_jiffies64(__ct) cputime_to_jiffies(__ct) #define jiffies64_to_cputime64(__jif) \ (__force cputime64_t)((__jif) * (NSEC_PER_SEC / HZ)) @@ -44,8 +48,13 @@ typedef u64 __nocast cputime64_t; /* * Convert cputime <-> microseconds */ -#define cputime_to_usecs(__ct) \ - ((__force u64)(__ct) / NSEC_PER_USEC) +static inline u64 cputime_to_usecs(const cputime_t ct) +{ + cputime_t __ct = ct; + + do_div(__ct, NSEC_PER_USEC); + return __ct; +} #define usecs_to_cputime(__usecs) \ (__force cputime_t)((__usecs) * NSEC_PER_USEC) #define usecs_to_cputime64(__usecs) \ @@ -54,8 +63,13 @@ typedef u64 __nocast cputime64_t; /* * Convert cputime <-> seconds */ -#define cputime_to_secs(__ct) \ - ((__force u64)(__ct) / NSEC_PER_SEC) +static inline u64 cputime_to_secs(const cputime_t ct) +{ + cputime_t __ct = ct; + + do_div(__ct, NSEC_PER_SEC); + return __ct; +} #define secs_to_cputime(__secs) \ (__force cputime_t)((__secs) * NSEC_PER_SEC) @@ -69,8 +83,10 @@ static inline cputime_t timespec_to_cputime(const struct timespec *val) } static inline void cputime_to_timespec(const cputime_t ct, struct timespec *val) { - val->tv_sec = (__force u64) ct / NSEC_PER_SEC; - val->tv_nsec = (__force u64) ct % NSEC_PER_SEC; + cputime_t __ct = ct; + + val->tv_nsec = do_div(__ct, NSEC_PER_SEC); + val->tv_sec = __ct; } /* @@ -83,15 +99,22 @@ static inline cputime_t timeval_to_cputime(struct timeval *val) } static inline void cputime_to_timeval(const cputime_t ct, struct timeval *val) { - val->tv_sec = (__force u64) ct / NSEC_PER_SEC; - val->tv_usec = ((__force u64) ct % NSEC_PER_SEC) / NSEC_PER_USEC; + cputime_t __ct = ct; + + val->tv_usec = do_div(__ct, NSEC_PER_SEC) / NSEC_PER_USEC; + val->tv_sec = __ct; } /* * Convert cputime <-> clock (USER_HZ) */ -#define cputime_to_clock_t(__ct) \ - ((__force u64)(__ct) / (NSEC_PER_SEC / USER_HZ)) +static inline u64 cputime_to_clock_t(const cputime_t ct) +{ + cputime_t __ct = ct; + + do_div(__ct, (NSEC_PER_SEC / USER_HZ)); + return __ct; +} #define clock_t_to_cputime(__x) \ (__force cputime_t)((__x) * (NSEC_PER_SEC / USER_HZ)) -- 1.8.1.2