Re: [PATCH v2 net-next] softirq: reduce latencies

On Fri, 2013-01-04 at 01:12 -0800, Joe Perches wrote:

On Fri, 2013-01-04 at 00:23 -0800, Eric Dumazet wrote:

quoted

On Fri, 2013-01-04 at 00:15 -0800, Joe Perches wrote:

quoted

Perhaps MAX_SOFTIRQ_TIME should be
#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
though it would be nicer if it were a compile time constant.

If you send a patch to convert msecs_to_jiffies() to an inline function
when HZ = 1000, I will gladly use it instead of (2*HZ/1000)

Right now, max(1, msecs_to_jiffies(2)) uses way too many instructions,
while it should be the constant 2, known at compile time.

Something like this might work.

This is incomplete, it just does msecs_to_jiffies,
and it should convert usecs_to_jiffies and the
jiffies_to_<foo> types too.

Maybe it's worthwhile.

It does reduce object size by 16 bytes per call site
(x86-32) when the argument is a constant. There are
about 800 of these jiffies conversions in kernel sources.

What do you think?

I think this is something to discuss in another thread, and definitely
worth to do, at least for msecs_to_jiffies()

We have many HZ references everywhere that could be cleaned up using
this.