From: tip-bot for Peter Zijlstra <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org,
peterz@infradead.org, tglx@linutronix.de
Subject: [tip:sched/core] sched/clock, x86: Move some cyc2ns() code around
Date: Mon, 13 Jan 2014 07:57:15 -0800 [thread overview]
Message-ID: <tip-01lslnavfgo3kmbo4532zlcj@git.kernel.org> (raw)
Commit-ID: 57c67da274f3fab38e08d2c9edf08b89e1d9c71d
Gitweb: http://git.kernel.org/tip/57c67da274f3fab38e08d2c9edf08b89e1d9c71d
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 29 Nov 2013 15:39:25 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 13 Jan 2014 13:47:39 +0100
sched/clock, x86: Move some cyc2ns() code around
There are no __cycles_2_ns() users outside of arch/x86/kernel/tsc.c,
so move it there.
There are no cycles_2_ns() users.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-01lslnavfgo3kmbo4532zlcj@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/timer.h | 59 -----------------------
arch/x86/kernel/tsc.c | 112 +++++++++++++++++++++++--------------------
2 files changed, 61 insertions(+), 110 deletions(-)
diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h
index 10a78c0..b4c6676 100644
--- a/arch/x86/include/asm/timer.h
+++ b/arch/x86/include/asm/timer.h
@@ -13,66 +13,7 @@ extern int recalibrate_cpu_khz(void);
extern int no_timer_check;
-/* Accelerators for sched_clock()
- * convert from cycles(64bits) => nanoseconds (64bits)
- * basic equation:
- * ns = cycles / (freq / ns_per_sec)
- * ns = cycles * (ns_per_sec / freq)
- * ns = cycles * (10^9 / (cpu_khz * 10^3))
- * ns = cycles * (10^6 / cpu_khz)
- *
- * Then we use scaling math (suggested by george@mvista.com) to get:
- * ns = cycles * (10^6 * SC / cpu_khz) / SC
- * ns = cycles * cyc2ns_scale / SC
- *
- * And since SC is a constant power of two, we can convert the div
- * into a shift.
- *
- * We can use khz divisor instead of mhz to keep a better precision, since
- * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
- * (mathieu.desnoyers@polymtl.ca)
- *
- * -johnstul@us.ibm.com "math is hard, lets go shopping!"
- *
- * In:
- *
- * ns = cycles * cyc2ns_scale / SC
- *
- * Although we may still have enough bits to store the value of ns,
- * in some cases, we may not have enough bits to store cycles * cyc2ns_scale,
- * leading to an incorrect result.
- *
- * To avoid this, we can decompose 'cycles' into quotient and remainder
- * of division by SC. Then,
- *
- * ns = (quot * SC + rem) * cyc2ns_scale / SC
- * = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC
- *
- * - sqazi@google.com
- */
-
DECLARE_PER_CPU(unsigned long, cyc2ns);
DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);
-#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
-
-static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
-{
- unsigned long long ns = this_cpu_read(cyc2ns_offset);
- ns += mul_u64_u32_shr(cyc, this_cpu_read(cyc2ns), CYC2NS_SCALE_FACTOR);
- return ns;
-}
-
-static inline unsigned long long cycles_2_ns(unsigned long long cyc)
-{
- unsigned long long ns;
- unsigned long flags;
-
- local_irq_save(flags);
- ns = __cycles_2_ns(cyc);
- local_irq_restore(flags);
-
- return ns;
-}
-
#endif /* _ASM_X86_TIMER_H */
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 930e5d4..b4a04ac 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -38,6 +38,66 @@ static int __read_mostly tsc_unstable;
static int __read_mostly tsc_disabled = -1;
int tsc_clocksource_reliable;
+
+/* Accelerators for sched_clock()
+ * convert from cycles(64bits) => nanoseconds (64bits)
+ * basic equation:
+ * ns = cycles / (freq / ns_per_sec)
+ * ns = cycles * (ns_per_sec / freq)
+ * ns = cycles * (10^9 / (cpu_khz * 10^3))
+ * ns = cycles * (10^6 / cpu_khz)
+ *
+ * Then we use scaling math (suggested by george@mvista.com) to get:
+ * ns = cycles * (10^6 * SC / cpu_khz) / SC
+ * ns = cycles * cyc2ns_scale / SC
+ *
+ * And since SC is a constant power of two, we can convert the div
+ * into a shift.
+ *
+ * We can use khz divisor instead of mhz to keep a better precision, since
+ * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
+ * (mathieu.desnoyers@polymtl.ca)
+ *
+ * -johnstul@us.ibm.com "math is hard, lets go shopping!"
+ */
+
+DEFINE_PER_CPU(unsigned long, cyc2ns);
+DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
+
+#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
+
+static inline unsigned long long cycles_2_ns(unsigned long long cyc)
+{
+ unsigned long long ns = this_cpu_read(cyc2ns_offset);
+ ns += mul_u64_u32_shr(cyc, this_cpu_read(cyc2ns), CYC2NS_SCALE_FACTOR);
+ return ns;
+}
+
+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
+{
+ unsigned long long tsc_now, ns_now, *offset;
+ unsigned long flags, *scale;
+
+ local_irq_save(flags);
+ sched_clock_idle_sleep_event();
+
+ scale = &per_cpu(cyc2ns, cpu);
+ offset = &per_cpu(cyc2ns_offset, cpu);
+
+ rdtscll(tsc_now);
+ ns_now = cycles_2_ns(tsc_now);
+
+ if (cpu_khz) {
+ *scale = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) +
+ cpu_khz / 2) / cpu_khz;
+ *offset = ns_now - mult_frac(tsc_now, *scale,
+ (1UL << CYC2NS_SCALE_FACTOR));
+ }
+
+ sched_clock_idle_wakeup_event(0);
+ local_irq_restore(flags);
+}
+
/*
* Scheduler clock - returns current time in nanosec units.
*/
@@ -62,7 +122,7 @@ u64 native_sched_clock(void)
rdtscll(this_offset);
/* return the value in ns */
- return __cycles_2_ns(this_offset);
+ return cycles_2_ns(this_offset);
}
/* We need to define a real function for sched_clock, to override the
@@ -589,56 +649,6 @@ int recalibrate_cpu_khz(void)
EXPORT_SYMBOL(recalibrate_cpu_khz);
-/* Accelerators for sched_clock()
- * convert from cycles(64bits) => nanoseconds (64bits)
- * basic equation:
- * ns = cycles / (freq / ns_per_sec)
- * ns = cycles * (ns_per_sec / freq)
- * ns = cycles * (10^9 / (cpu_khz * 10^3))
- * ns = cycles * (10^6 / cpu_khz)
- *
- * Then we use scaling math (suggested by george@mvista.com) to get:
- * ns = cycles * (10^6 * SC / cpu_khz) / SC
- * ns = cycles * cyc2ns_scale / SC
- *
- * And since SC is a constant power of two, we can convert the div
- * into a shift.
- *
- * We can use khz divisor instead of mhz to keep a better precision, since
- * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
- * (mathieu.desnoyers@polymtl.ca)
- *
- * -johnstul@us.ibm.com "math is hard, lets go shopping!"
- */
-
-DEFINE_PER_CPU(unsigned long, cyc2ns);
-DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
-
-static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
-{
- unsigned long long tsc_now, ns_now, *offset;
- unsigned long flags, *scale;
-
- local_irq_save(flags);
- sched_clock_idle_sleep_event();
-
- scale = &per_cpu(cyc2ns, cpu);
- offset = &per_cpu(cyc2ns_offset, cpu);
-
- rdtscll(tsc_now);
- ns_now = __cycles_2_ns(tsc_now);
-
- if (cpu_khz) {
- *scale = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) +
- cpu_khz / 2) / cpu_khz;
- *offset = ns_now - mult_frac(tsc_now, *scale,
- (1UL << CYC2NS_SCALE_FACTOR));
- }
-
- sched_clock_idle_wakeup_event(0);
- local_irq_restore(flags);
-}
-
static unsigned long long cyc2ns_suspend;
void tsc_save_sched_clock_state(void)
reply other threads:[~2014-01-13 15:57 UTC|newest]
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