Messages in this thread | | | Date | Tue, 30 Oct 2012 08:14:22 -0700 | From | Dave Hansen <> | Subject | Re: [PATCH] mm: memmap_init_zone() performance improvement |
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On 10/20/2012 01:29 AM, Mel Gorman wrote: > I'm travelling at the moment so apologies that I have not followed up on > this. My problem is still the same with the patch - it changes more > headers than is necessary and it is sparsemem specific. At minimum, try > the suggestion of > > if (!early_pfn_valid(pfn)) { > pfn = ALIGN(pfn + MAX_ORDER_NR_PAGES, MAX_ORDER_NR_PAGES) - 1; > continue; > }
Sorry I didn't catch this until v2...
Is that ALIGN() correct? If pfn=3, then it would expand to:
(3+MAX_ORDER_NR_PAGES+MAX_ORDER_NR_PAGES-1) & ~(MAX_ORDER_NR_PAGES-1)
You would end up skipping the current MAX_ORDER_NR_PAGES area, and then one _extra_ because ALIGN() aligns up, and you're adding MAX_ORDER_NR_PAGES too. It doesn't matter unless you run in to a !early_valid_pfn() in the middle of a MAX_ORDER area, I guess.
I think this would work, plus be a bit smaller:
pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES) - 1;
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