On Tue, Oct 28, 2008 at 09:30:10AM -0600, Grant Likely wrote: > 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. Yes, that 'irq' array might as well be part of the same structure. -- 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
