On 11/21/2016 3:54 AM, Ingo Molnar wrote:
* John Stultz <[email protected]> wrote:
From: Chris Metcalf <[email protected]>
The "cycles" argument should not be an absolute clocksource cycle
value, as the implementation's arithmetic will overflow relatively
easily with wide (64 bit) clocksource counters.
For performance, the implementation is simple and fast, since the
function is intended for only relatively small delta values of
clocksource cycles.
Cc: Richard Cochran <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Chris Metcalf <[email protected]>
[jstultz: Fixed up to merge against HEAD & commit message tweaks]
Signed-off-by: John Stultz <[email protected]>
---
include/linux/clocksource.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0839818..0881bca 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -169,7 +169,10 @@ static inline u32 clocksource_hz2mult(u32 hz, u32
shift_constant)
* @mult: cycle to nanosecond multiplier
* @shift: cycle to nanosecond divisor (power of two)
*
- * Converts cycles to nanoseconds, using the given mult and shift.
+ * Converts clocksource cycles to nanoseconds, using the given mult and shift.
+ * The code is optimized for performance and not intended to work
+ * with absolute clocksource cycles, as it will easily overflow,
+ * but just intended for relative (delta) clocksource cycles.
Had to read this explanation twice, how about:
* Converts clocksource cycles to nanoseconds, using the given @mult and
@shift.
* The code is optimized for performance and is not intended to work
* with absolute clocksource cycles (as those will easily overflow),
* but is only intended to be used with relative (delta) clocksource cycles.
Did I get it right?
Yes, I think that's an improvement. Thanks!
John, I assume you can just fix this up?
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
