Updated the patch for improved readability.
How about the following patch?
To apply proper slack, the original algorithm used to prepare a mask and
then apply the mask to obtain the appropriately rounded-off absolute
time the timer expires.
This patch modifies the masking logic to a bit-shift logic, therby
reducing the complexity and number of operations. Thus obtaining a minor
speed-up.
Signed-off-by: Chinmay V S <[email protected]>
---
kernel/timer.c | 9 +++------
1 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c
index a297ffc..eb4b708 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -785,9 +785,7 @@ EXPORT_SYMBOL(mod_timer_pending);
* Algorithm:
* 1) calculate the maximum (absolute) time
* 2) calculate the highest bit where the expires and new max are different
- * 3) use this bit to make a mask
- * 4) use the bitmask to round down the maximum time, so that all last
- * bits are zeros
+ * 3) round down the maximum time, so that all the lower bits are zeros
*/
static inline
unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
@@ -811,9 +809,8 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
bit = find_last_bit(&mask, BITS_PER_LONG);
- mask = (1 << bit) - 1;
-
- expires_limit = expires_limit & ~(mask);
+ /* Round down by zero-ing the lower bits */
+ expires_limit = (expires_limit >> bit) << bit;
return expires_limit;
}
--
1.7.5.4
* Chinmay V S | 2012-02-03 21:30:50 [+0530]:
>Updated the patch for improved readability.
Arjan's point was that this is not critical for performance and as such
it does not need an improvement.
>How about the following patch?
I guess this will be left as is.
Sebastian