Messages in this thread |  | | Date | Thu, 5 Apr 2018 04:34:44 -0700 | From | Matthew Wilcox <> | Subject | Re: [PATCH v7 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() |
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On Thu, Apr 05, 2018 at 01:04:35AM -0700, Jia He wrote: > Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns > where possible") optimized the loop in memmap_init_zone(). But there is > still some room for improvement. E.g. if pfn and pfn+1 are in the same > memblock region, we can simply pfn++ instead of doing the binary search > in memblock_next_valid_pfn.
Sure, but I bet if we are >end_pfn, we're almost certainly going to the start_pfn of the next block, so why not test that as well?
> + /* fast path, return pfn+1 if next pfn is in the same region */ > + if (early_region_idx != -1) { > + start_pfn = PFN_DOWN(regions[early_region_idx].base); > + end_pfn = PFN_DOWN(regions[early_region_idx].base + > + regions[early_region_idx].size); > + > + if (pfn >= start_pfn && pfn < end_pfn) > + return pfn;
early_region_idx++; start_pfn = PFN_DOWN(regions[early_region_idx].base); if (pfn >= end_pfn && pfn <= start_pfn) return start_pfn; > + }
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