[RESEND PATCH v10 6/6] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()

On 8/16/18 9:35 PM, Pasha Tatashin wrote:

On 7/6/18 5:01 AM, Jia He wrote:

quoted

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. in early_pfn_valid(), if pfn and
pfn+1 are in the same memblock region, we can record the last returned
memblock region index and check whether pfn++ is still in the same
region.

Currently it only improve the performance on arm/arm64 and will have no
impact on other arches.

For the performance improvement, after this set, I can see the time
overhead of memmap_init() is reduced from 27956us to 13537us in my
armv8a server(QDF2400 with 96G memory, pagesize 64k).

This series would be a lot simpler if patches 4, 5, and 6 were dropped.
The extra complexity does not make sense to save 0.0001s/T during not.

s/not/boot

Patches 1-3, look OK, but without patches 4-5 __init_memblock should be
made local static as I suggested earlier.

s/__init_memblock/early_region_idx