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

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


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