Messages in this thread | | | Date | Mon, 12 Mar 2007 04:12:32 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [QUICKLIST 0/6] Arch independent quicklists V1 |
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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.
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