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[PATCH 01/37] jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY

From Frederic Weisbecker <fweisbec@gmail.com>
Newsgroups linux.kernel
Subject [PATCH 01/37] jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY
Date 2017-01-22 19:30 +0100
Message-ID <t2v3R-4ap-47@gated-at.bofh.it> (permalink)
References <t2v3P-4ap-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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NSEC_PER_JIFFY is an ad-hoc redefinition of TICK_NSEC. Let's rather
use a unique and well maintained version.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/time/jiffies.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index a4a0e47..7906b3f 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -27,19 +27,8 @@
 
 #include "timekeeping.h"
 
-/* The Jiffies based clocksource is the lowest common
- * denominator clock source which should function on
- * all systems. It has the same coarse resolution as
- * the timer interrupt frequency HZ and it suffers
- * inaccuracies caused by missed or lost timer
- * interrupts and the inability for the timer
- * interrupt hardware to accuratly tick at the
- * requested HZ value. It is also not recommended
- * for "tick-less" systems.
- */
-#define NSEC_PER_JIFFY	((NSEC_PER_SEC+HZ/2)/HZ)
 
-/* Since jiffies uses a simple NSEC_PER_JIFFY multiplier
+/* Since jiffies uses a simple TICK_NSEC multiplier
  * conversion, the .shift value could be zero. However
  * this would make NTP adjustments impossible as they are
  * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
@@ -47,8 +36,8 @@
  * amount, and give ntp adjustments in units of 1/2^8
  *
  * The value 8 is somewhat carefully chosen, as anything
- * larger can result in overflows. NSEC_PER_JIFFY grows as
- * HZ shrinks, so values greater than 8 overflow 32bits when
+ * larger can result in overflows. TICK_NSEC grows as HZ
+ * shrinks, so values greater than 8 overflow 32bits when
  * HZ=100.
  */
 #if HZ < 34
@@ -64,12 +53,23 @@ static u64 jiffies_read(struct clocksource *cs)
 	return (u64) jiffies;
 }
 
+/*
+ * The Jiffies based clocksource is the lowest common
+ * denominator clock source which should function on
+ * all systems. It has the same coarse resolution as
+ * the timer interrupt frequency HZ and it suffers
+ * inaccuracies caused by missed or lost timer
+ * interrupts and the inability for the timer
+ * interrupt hardware to accuratly tick at the
+ * requested HZ value. It is also not recommended
+ * for "tick-less" systems.
+ */
 static struct clocksource clocksource_jiffies = {
 	.name		= "jiffies",
 	.rating		= 1, /* lowest valid rating*/
 	.read		= jiffies_read,
 	.mask		= CLOCKSOURCE_MASK(32),
-	.mult		= NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
+	.mult		= TICK_NSEC << JIFFIES_SHIFT, /* details above */
 	.shift		= JIFFIES_SHIFT,
 	.max_cycles	= 10,
 };
@@ -125,7 +125,7 @@ int register_refined_jiffies(long cycles_per_second)
 	shift_hz += cycles_per_tick/2;
 	do_div(shift_hz, cycles_per_tick);
 	/* Calculate nsec_per_tick using shift_hz */
-	nsec_per_tick = (u64)NSEC_PER_SEC << 8;
+	nsec_per_tick = (u64)TICK_NSEC << 8;
 	nsec_per_tick += (u32)shift_hz/2;
 	do_div(nsec_per_tick, (u32)shift_hz);
 
-- 
2.7.4

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[PATCH 00/37] cputime: Convert core use of cputime_t to nsecs v3 Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 12/37] binfmt: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 16/37] signal: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 26/37] cputime: Complete nsec conversion of tick based accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 36/37] cputime: Remove asm generic headers Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 09/37] alpha: Convert obsolete cputime_t to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 30/37] ia64: Convert vtime to use nsec units directly Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 04/37] cputime: Convert kcpustat to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
    Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Stanislaw Gruszka <sgruszka@redhat.com> - 2017-01-28 13:20 +0100
      Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-28 16:40 +0100
        Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Stanislaw Gruszka <sgruszka@redhat.com> - 2017-01-30 15:00 +0100
          Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-30 16:40 +0100
  [PATCH 33/37] powerpc: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 07/37] cputime: Special API to return old-typed cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 28/37] cputime: Remove jiffies based cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 03/37] sched: Remove unused INIT_CPUTIME macro Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 10/37] x86: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 20/37] itimer: Convert internal cputime_t units to nsec Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 13/37] acct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 05/37] macintosh/rack-meter: Remove cputime_t internal use Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 24/37] cputime: Push time to account_idle_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 34/37] s390: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 01/37] jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 29/37] ia64: Move nsecs based cputime headers to the last arch using it Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 37/37] s390: Prevent from cputime leaks Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
    Re: [PATCH 37/37] s390: Prevent from cputime leaks Martin Schwidefsky <schwidefsky@de.ibm.com> - 2017-01-23 10:50 +0100
      Re: [PATCH 37/37] s390: Prevent from cputime leaks Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-25 16:30 +0100
        Re: [PATCH 37/37] s390: Prevent from cputime leaks Martin Schwidefsky <schwidefsky@de.ibm.com> - 2017-01-25 16:50 +0100
  [PATCH 27/37] vtime: Return nsecs instead of cputime_t to account Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 32/37] s390: Make arch_cpu_idle_time() to return nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 31/37] ia64: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 18/37] posix-timers: Use TICK_NSEC instead of a dynamically ad-hoc calculated version Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 02/37] time: Introduce jiffies64_to_nsecs() Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 15/37] tsacct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 14/37] delaycct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 25/37] cputime: Push time to account_system_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 23/37] cputime: Push time to account_steal_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 35/37] cputime: Remove unused nsec_to_cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 19/37] posix-timers: Convert internals to use nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 17/37] cputime: Increment kcpustat directly on irqtime account Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
  [PATCH 06/37] cputime: Convert guest time accounting to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100

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