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time/sched_clock: Round the frequency reported to nearest rather than down

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The frequency reported for clock sources are rounded down, which gives
misleading figures, e.g.:

 I/O ASIC clock frequency 24999480Hz
 sched_clock: 32 bits at 24MHz, resolution 40ns, wraps every 85901132779ns
 MIPS counter frequency 59998512Hz
 sched_clock: 32 bits at 59MHz, resolution 16ns, wraps every 35792281591ns

Rounding to nearest is more adequate:

 I/O ASIC clock frequency 24999664Hz
 sched_clock: 32 bits at 25MHz, resolution 40ns, wraps every 85900499947ns
 MIPS counter frequency 59999728Hz
 sched_clock: 32 bits at 60MHz, resolution 16ns, wraps every 35791556599ns

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2204240055590.9383@angie.orcam.me.uk
This commit is contained in:
Maciej W. Rozycki 2022-04-24 12:47:20 +01:00 committed by Thomas Gleixner
parent 90be8d6c1f
commit 92067440f1
1 changed files with 3 additions and 2 deletions
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5
kernel/time/sched_clock.c
View file

@ -8,6 +8,7 @@
#include <linux/jiffies.h>
#include <linux/ktime.h>
#include <linux/kernel.h>
#include <linux/math.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
@ -199,11 +200,11 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
r = rate;
if (r >= 4000000) {
r /= 1000000;
r = DIV_ROUND_CLOSEST(r, 1000000);
r_unit = 'M';
} else {
if (r >= 1000) {
r /= 1000;
r = DIV_ROUND_CLOSEST(r, 1000);
r_unit = 'k';
} else {
r_unit = ' ';