On Sun, 2010-02-28 at 00:14 +0000, Benjamin Herrenschmidt wrote: > On Fri, 2010-02-26 at 21:00 +0000, Russell King - ARM Linux wrote: > > On Fri, Feb 26, 2010 at 04:25:21PM +0000, Catalin Marinas wrote: > > > For mmap'ed pages (and present in the page cache), is it guaranteed that > > > the HCD driver won't write to it once it has been mapped into user > > > space? If that's the case, it may solve the problem by just reversing > > > the meaning of PG_arch_1 on ARM and assume that a newly allocated page > > > has dirty D-cache by default. > > > > I guess we could also set PG_arch_1 in the DMA API as well, to avoid the > > unnecessary D cache flushing when clean pages get mapped into userspace. That sounds good to me. > That's an interesting thought for us too. When doing I$/D$ coherency, we > have to fist flush the D$ and then invalidate the I$. If we could keep > track of D$ and I$ separately, we could avoid the first step in many > cases, including the DMA API trick you mentioned. > > I wonder if it's time to get a PG_arch_2 :-) As an optimisation, I think this would help (rather than always invalidating the I-cache in update_mmu_cache or set_pte_at). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
