Messages in this thread Patch in this message | | | From | Chinmay V S <> | Subject | [RFC] [PATCH] [timer] Optimise apply_slack() for size and speed. | Date | Tue, 31 Jan 2012 15:07:32 +0530 |
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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 <chinmay.v.s@pathpartnertech.com> --- kernel/timer.c | 8 ++------ 1 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c index a297ffc..0379658 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 +809,7 @@ 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); + expires_limit = (expires_limit >> bit) << bit; return expires_limit; } -- 1.7.5.4
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