Messages in this thread |  | | Subject | Re: [PATCH v7 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() | From | Jia He <> | Date | Thu, 5 Apr 2018 20:44:12 +0800 |
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On 4/5/2018 7:34 PM, Matthew Wilcox Wrote: > 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; Thanks, thus the binary search in next step can be discarded?
-- Cheers, Jia
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