A respin of of the series to address these issues: - fix issues found by kbuild - find_alloc_contig_pages() should take nr_pages as argument instead of page order (Vlastimil and Michal). - Cleaned up migratetype handling (Vlastimil and Michal). - Use pfn_to_online_page instead of pfn_to_page as suggested by Michal. Also added comment about minimal number of conditions checked in contig_pfn_range_valid(). - When scanning pfns in zone, take pgdat_resize_lock() instead of zone->lock (Michal) Also, - Separate patch to change type of free_contig_range(nr_pages) to an unsigned long so that it is consistent with other uses of nr_pages. - Separate patch to optionally validate migratetype during pageblock isolation. - Make find_alloc_contig_pages() work for smaller size allocation by simply calling __alloc_pages_nodemask(). Vlastimil and Michal brought up the issue of allocation alignment. The routine will currently align to 'nr_pages' (which is the requested size argument). It does this by examining and trying to allocate the first nr_pages aligned/nr_pages sized range. If this fails, it moves on to the next nr_pages aligned/nr_pages sized range until success or all potential ranges are exhausted. If we allow an alignment to be specified, we will need to potentially check all alignment aligned/nr_pages sized ranges. In the worst case where alignment = PAGE_SIZE, this could result in huge increase in the number of ranges to check. To help cut down on the number of ranges to check, we could identify the first page that causes a range allocation failure and start the next range at the next aligned boundary. I tried this, and we still end up with a huge number of ranges and wasted CPU cycles. This series did not add an alignment option. Allocations are aligned to nr_pages as described above. If someone can thing of a good way to support an alignment argument, I am open to implementing/adding it. As described before, These patches came out of the "[RFC] mmap(MAP_CONTIG)" discussions at: http://lkml.kernel.org/r/21f1ec96-2822-1189-1c95-79a2bb491571@xxxxxxxxxx One suggestion in that thread was to create a friendlier interface that could be used by drivers and others outside core mm code to allocate a contiguous set of pages. The alloc_contig_range() interface is used for this purpose today by CMA and gigantic page allocation. However, this is not a general purpose interface. So, wrap alloc_contig_range() in the more general interface: struct page *find_alloc_contig_pages(unsigned long nr_pages, gfp_t gfp, int nid, nodemask_t *nodemask) This interface is essentially the same functionality provided by the hugetlb specific routine alloc_gigantic_page(). After creating the interface, change alloc_gigantic_page() to call find_alloc_contig_pages() and delete all the supporting code in hugetlb.c. A new use case for allocating contiguous memory has been identified in Intel(R) Resource Director Technology Cache Pseudo-Locking. Mike Kravetz (4): mm: change type of free_contig_range(nr_pages) to unsigned long mm: check for proper migrate type during isolation mm: add find_alloc_contig_pages() interface mm/hugetlb: use find_alloc_contig_pages() to allocate gigantic pages include/linux/gfp.h | 14 +++- include/linux/page-isolation.h | 8 +-- mm/cma.c | 2 +- mm/hugetlb.c | 87 ++-------------------- mm/memory_hotplug.c | 2 +- mm/page_alloc.c | 159 +++++++++++++++++++++++++++++++++++++---- mm/page_isolation.c | 40 ++++++++--- 7 files changed, 200 insertions(+), 112 deletions(-) -- 2.13.6
