Re: [PATCH resend5 4/4] cputime: optimize jiffies_to_cputime(1)

[Thomas Gleixner <tglx@linutronix.de>]

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@redhat.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
>