On Sun, 11 Mar 2007, David Miller wrote: > I'm going to make the radical declaration that it be perhaps often > better to always initialize page table chunks to all zeros on > allocation.
That is the case if most of the page is going to be used soon. If we have sparse access patterns then not zeroing can avoid uselessly bringing cachelines in. > The reason is that every time I've monitored the allocation patterns > of these things on SMP, the page table chunks always get released on a > different cpu than where they were initialized. But its even advantageous in that case for sparse allocs. > The allocator side just does nothing but emit L2 cache line ownership > transactions as the pte page is touched. Especially on chips like > PowerPC where zero initialization is absurdly cheap, we can avoid all > of the cache line transfers if we just initialize it at allocation > time. We have no need to touch all the cache lines w/o initialization if we alloc from the quicklist. And that is a performance benefit. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
