On Thu, 2015-12-31 at 23:58 -0800, Mike Danese wrote:
> We can reduce the number of operations performed by icmp_global_allow
> and make the routine more readable by refactoring it in two ways:
>
> First, this patch refactors the meaning of the "delta" variable. Before
> this change, it meant min("time since last refill of token bucket", HZ).
> After this change, it means "time since last refill". The original
> definition is required only once but was being calculated twice. The new
> meaning is also more intuitive for a variable named "delta".
>
> Second, by calculating "delta" (time since last refill of token bucket)
> and "cbr" (token bucket can be refilled) at the beginning of the
> routine, we reduce the number of repeated calculations of these two
> variables.
>
> There should be no functional difference.
>
> Signed-off-by: Mike Danese <mikedan...@google.com>
> ---
> net/ipv4/icmp.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
Hi Mike
Sorry, this is a very broken patch.
There is a comment you apparently missed completely :
/* Check if token bucket is empty and cannot be refilled
* without taking the spinlock.
*/
There is a reason we compute 'delta' two times.
One without the spinlock held, and a second time with the spinlock held.
This is an opportunistic way to exit early without false sharing in the
stress case where many cpus might enter this code.
Really I do not think current code needs any 'refactoring', especially
around December 31th at midnight ;)
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