On Tue, Oct 28, 2008 at 9:17 AM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Tue, Oct 28, 2008 at 07:08:06AM -0600, Grant Likely wrote: >> On Tue, Oct 28, 2008 at 1:46 AM, Paulius Zaleckas >> <paulius.zaleckas@xxxxxxxxxxxx> wrote: >> > Grant Likely wrote: >> >> The IRQ array is fixed size. You can add it to the mdio_gpio_info >> >> structure and then just set the pointer here so that only one kzalloc >> >> is needed. >> > >> > It can be put in mdio_gpio_info, but please note that mdio_gpio_info is >> > allocated with kzalloc() and irq with kmalloc(), because there is no need >> > to fill this array with zeros(see below). >> >> Adding an additional 32 words to be zeroed in the mdio_gpio_info >> kzalloc is considerably cheaper than doing an additional kmalloc. >> Plus, once the array is zeroed it is then in the cache and so the >> filling it with -1 also becomes cheaper. > > Actually no, it doesn't become cheaper. You're making the assumption > that cache lines are allocated when memory is written to. This isn't > the case with the vast majority of ARM CPUs. Okay, I wasn't aware of that on ARM. However it is still true that increasing the size of the kzalloc is cheaper than doing 2 allocs. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
