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Date: Fri, 29 May 2009 14:09:08 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Stanislaw Gruszka <sgruszka@...hat.com>
cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Oleg Nesterov <oleg@...hat.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Paul Mackerras <paulus@...ba.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH resend5 4/4] cputime: optimize jiffies_to_cputime(1)
On Fri, 29 May 2009, Stanislaw Gruszka wrote:
> For powerpc with CONFIG_VIRT_CPU_ACCOUNTING jiffies_to_cputime(1) is not
> compile time constant and run time calculations are quite expensive. To
> optimize we use precomputed value. For all other architectures is is
> preprocessor definition.
Can the PowerPC folks please have a look at this ?
Thanks,
tglx
> Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
> ---
> This patch (with 3 previous) was compiled on x86, x86_64, ppc with
> CONFIG_VIRT_CPU_ACCOUNTNG=n, ppc64 with CONFIG_VIRT_CPU_ACCOUNTING=y.
> Run time testing was done only on x86.
>
> arch/ia64/include/asm/cputime.h | 1 +
> arch/powerpc/include/asm/cputime.h | 13 +++++++++++++
> arch/powerpc/kernel/time.c | 4 ++++
> arch/s390/include/asm/cputime.h | 1 +
> include/asm-generic/cputime.h | 1 +
> kernel/itimer.c | 4 ++--
> kernel/posix-cpu-timers.c | 6 +++---
> kernel/sched.c | 9 ++++-----
> 8 files changed, 29 insertions(+), 10 deletions(-)
>
> diff --git a/arch/ia64/include/asm/cputime.h b/arch/ia64/include/asm/cputime.h
> index d20b998..7fa8a85 100644
> --- a/arch/ia64/include/asm/cputime.h
> +++ b/arch/ia64/include/asm/cputime.h
> @@ -30,6 +30,7 @@ typedef u64 cputime_t;
> typedef u64 cputime64_t;
>
> #define cputime_zero ((cputime_t)0)
> +#define cputime_one_jiffy jiffies_to_cputime(1)
> #define cputime_max ((~((cputime_t)0) >> 1) - 1)
> #define cputime_add(__a, __b) ((__a) + (__b))
> #define cputime_sub(__a, __b) ((__a) - (__b))
> diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
> index f42e623..fa19f3f 100644
> --- a/arch/powerpc/include/asm/cputime.h
> +++ b/arch/powerpc/include/asm/cputime.h
> @@ -18,6 +18,9 @@
>
> #ifndef CONFIG_VIRT_CPU_ACCOUNTING
> #include <asm-generic/cputime.h>
> +#ifdef __KERNEL__
> +static inline void setup_cputime_one_jiffy(void) { }
> +#endif
> #else
>
> #include <linux/types.h>
> @@ -49,6 +52,11 @@ typedef u64 cputime64_t;
> #ifdef __KERNEL__
>
> /*
> + * One jiffy in timebase units computed during initialization
> + */
> +extern cputime_t cputime_one_jiffy;
> +
> +/*
> * Convert cputime <-> jiffies
> */
> extern u64 __cputime_jiffies_factor;
> @@ -89,6 +97,11 @@ static inline cputime_t jiffies_to_cputime(const unsigned long jif)
> return ct;
> }
>
> +static inline void setup_cputime_one_jiffy(void)
> +{
> + cputime_one_jiffy = jiffies_to_cputime(1);
> +}
> +
> static inline cputime64_t jiffies64_to_cputime64(const u64 jif)
> {
> cputime_t ct;
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index 48571ac..8549edc 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -191,6 +191,8 @@ EXPORT_SYMBOL(__cputime_clockt_factor);
> DEFINE_PER_CPU(unsigned long, cputime_last_delta);
> DEFINE_PER_CPU(unsigned long, cputime_scaled_last_delta);
>
> +cputime_t cputime_one_jiffy;
> +
> static void calc_cputime_factors(void)
> {
> struct div_result res;
> @@ -498,6 +500,7 @@ static int __init iSeries_tb_recal(void)
> tb_to_xs = divres.result_low;
> vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
> vdso_data->tb_to_xs = tb_to_xs;
> + setup_cputime_one_jiffy();
> }
> else {
> printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
> @@ -904,6 +907,7 @@ void __init time_init(void)
> tb_ticks_per_usec = ppc_tb_freq / 1000000;
> tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
> calc_cputime_factors();
> + setup_cputime_one_jiffy();
>
> /*
> * Calculate the length of each tick in ns. It will not be
> diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
> index 941384f..ea52754 100644
> --- a/arch/s390/include/asm/cputime.h
> +++ b/arch/s390/include/asm/cputime.h
> @@ -39,6 +39,7 @@ __div(unsigned long long n, unsigned int base)
> #endif /* __s390x__ */
>
> #define cputime_zero (0ULL)
> +#define cputime_one_jiffy jiffies_to_cputime(1)
> #define cputime_max ((~0UL >> 1) - 1)
> #define cputime_add(__a, __b) ((__a) + (__b))
> #define cputime_sub(__a, __b) ((__a) - (__b))
> diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
> index 1c1fa42..ca0f239 100644
> --- a/include/asm-generic/cputime.h
> +++ b/include/asm-generic/cputime.h
> @@ -7,6 +7,7 @@
> typedef unsigned long cputime_t;
>
> #define cputime_zero (0UL)
> +#define cputime_one_jiffy jiffies_to_cputime(1)
> #define cputime_max ((~0UL >> 1) - 1)
> #define cputime_add(__a, __b) ((__a) + (__b))
> #define cputime_sub(__a, __b) ((__a) - (__b))
> diff --git a/kernel/itimer.c b/kernel/itimer.c
> index 21adff7..8078a32 100644
> --- a/kernel/itimer.c
> +++ b/kernel/itimer.c
> @@ -64,7 +64,7 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
>
> if (cputime_le(cval, t))
> /* about to fire */
> - cval = jiffies_to_cputime(1);
> + cval = cputime_one_jiffy;
> else
> cval = cputime_sub(cval, t);
> }
> @@ -161,7 +161,7 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
> if (!cputime_eq(cval, cputime_zero) ||
> !cputime_eq(nval, cputime_zero)) {
> if (cputime_gt(nval, cputime_zero))
> - nval = cputime_add(nval, jiffies_to_cputime(1));
> + nval = cputime_add(nval, cputime_one_jiffy);
> set_process_cpu_timer(tsk, clock_id, &nval, &cval);
> }
> it->expires = nval;
> diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> index 69c9237..18bdde6 100644
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -1086,7 +1086,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
> it->error += it->incr_error;
> if (it->error >= onecputick) {
> it->expires = cputime_sub(it->expires,
> - jiffies_to_cputime(1));
> + cputime_one_jiffy);
> it->error -= onecputick;
> }
> } else
> @@ -1461,7 +1461,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
> if (!cputime_eq(*oldval, cputime_zero)) {
> if (cputime_le(*oldval, now.cpu)) {
> /* Just about to fire. */
> - *oldval = jiffies_to_cputime(1);
> + *oldval = cputime_one_jiffy;
> } else {
> *oldval = cputime_sub(*oldval, now.cpu);
> }
> @@ -1712,7 +1712,7 @@ static __init int init_posix_cpu_timers(void)
> register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
> register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
>
> - cputime_to_timespec(jiffies_to_cputime(1), &ts);
> + cputime_to_timespec(cputime_one_jiffy, &ts);
> onecputick = ts.tv_nsec;
> WARN_ON(ts.tv_sec != 0);
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 26efa47..954803e 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4726,17 +4726,16 @@ void account_idle_time(cputime_t cputime)
> */
> void account_process_tick(struct task_struct *p, int user_tick)
> {
> - cputime_t one_jiffy = jiffies_to_cputime(1);
> - cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
> + cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
> struct rq *rq = this_rq();
>
> if (user_tick)
> - account_user_time(p, one_jiffy, one_jiffy_scaled);
> + account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
> else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
> - account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
> + account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
> one_jiffy_scaled);
> else
> - account_idle_time(one_jiffy);
> + account_idle_time(cputime_one_jiffy);
> }
>
> /*
> --
> 1.5.5.6
>
--
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