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>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-5-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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 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 @@
#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 @@
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 eae4511..211d7b0 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -193,6 +193,8 @@
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;
@@ -500,6 +502,7 @@
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"
@@ -945,6 +948,7 @@
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 7a3817a..24b1244 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -42,6 +42,7 @@
#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 @@
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 @@
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 69c9237435..18bdde6 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1086,7 +1086,7 @@
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 @@
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 @@
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 1b59e26..8f977d5 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5031,17 +5031,16 @@
*/
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);
}
/*
