On Sat, 2011-03-12 at 12:08 -0500, John David Anglin wrote: > The attached change fixes the "SLOW!" timer_interrupt warning that I > occassionally see on my rp3440 (800 MHz). We need to avoid using the > expensive div/mul method. I have seen instances where it takes more > than 0x7000 cycles. > Signed-off-by: John David Anglin <dave.anglin@xxxxxxxxxxxxxx> > > Dave Your change implies that more than 2^6 == 64 ticks (that's over half a second) can have elapsed between two calls to timer_interrupt(). That looks like an awfully large lacuna, and is like the cause of whatever problem you're seeing rather than the use of divide. Parisc even has the DS instruction that would seem to make division not so expensive. How much more expensive is div than mul? because if it's a lot more, we can use a logarithmic iteration to do the division. James -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
