On Thu, 2010-03-04 at 18:07 +0000, Catalin Marinas wrote: > > Are you more in favour if a PIO kmap API than inverting the meaning of > PG_arch_1? My main worry with this approach is the sheer amount of drivers that need fixing. I believe inverting PG_arch_1 is a better solution and I somewhat fail to see how we end up doing too much flushing if we have per-page execute permission (but maybe SH doesn't ?) > I'm not familiar with SH but for PIO devices the flushing shouldn't be > more aggressive. For the DMA devices, Russell suggested that we mark > the > page as clean (set PG_dcache_clean) in the DMA API to avoid the > default > flushing. I really like that idea, as I said earlier, but I'm worried about the I$ side of things. IE. What I'm trying to say is that I can't see how to do that optimisation without ending up with missing I$ invalidations or doing way too many of them, unless we have a separate bit to track I$ state. > > Note that the PG_dcache_dirty semantics are also outlined in > > Documentation/cachetlb.txt for PG_arch_1 usage, so it's hardly > esoteric. > > Yes, but the flush_dcache_page() semantics outlined in the same file > aren't followed by all the PIO drivers in the kernel. > Cheers, Ben. -- 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
