On Mon, Dec 09, 2013 at 10:56:46AM -0800, Joe Perches wrote: > On Mon, 2013-12-09 at 19:44 +0100, Frederic Weisbecker wrote: > > On Sun, Nov 17, 2013 at 01:55:10AM -0800, Joe Perches wrote: > > > Possible speed improvement of the __do_softirq function by using ffs > > > instead of using a while loop with an & 1 test then single bit shift. > [] > > Perhaps using for_each_set_bit() would simplify that more? > > It might simplify the appearance of the code but it > would/could expand the amount of generated code because > for_each_set_bit uses an address_of(unsigned long) and > the value tested is an unsigned int. > > extra dereferences, can't be in a register, etc...
I'm not sure that would matter that much. But yeah it appears that find_first_bit/find_next_bit aren't even overriden in x86. So they are function calls. Although I guess that most of the time only one softirq is pending at a time. But anyway perhaps we want that path to stay very optimized, so you're patch look ok. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
