v1 -> v2: - Adressed feedback by Michal - Restrict the allocation to a node with __GFP_THISNODE - Drop PageHuge check in alloc_and_dissolve_huge_page - Re-order comments in isolate_or_dissolve_huge_page - Extend comment in isolate_migratepages_block - Place put_page right after we got the page, otherwise dissolve_free_huge_page will fail RFC -> v1: - Drop RFC - Addressed feedback from David and Mike - Fence off gigantic pages as there is a cyclic dependency between them and alloc_contig_range - Re-organize the code to make race-window smaller and to put all details in hugetlb code - Drop nodemask initialization. First a node will be tried and then we will back to other nodes containing memory (N_MEMORY). Details in patch#1's changelog - Count new page as surplus in case we failed to dissolve the old page and the new one. Details in patch#1. Cover letter: alloc_contig_range lacks the hability for handling HugeTLB pages. This can be problematic for some users, e.g: CMA and virtio-mem, where those users will fail the call if alloc_contig_range ever sees a HugeTLB page, even when those pages lay in ZONE_MOVABLE and are free. That problem can be easily solved by replacing the hugepage by allocating a new one and dissolving the old one. In-use HugeTLB are no exception though, as those can be isolated and migrated as any other LRU or Movable page. This patchset aims for improving alloc_contig_range->isolate_migratepages_block, so HugeTLB pages can be recognized and handled. Below is an insight from David (thanks), where the problem can clearly be seen: "Start a VM with 4G. Hotplug 1G via virtio-mem and online it to ZONE_MOVABLE. Allocate 512 huge pages. [root@localhost ~]# cat /proc/meminfo MemTotal: 5061512 kB MemFree: 3319396 kB MemAvailable: 3457144 kB ... HugePages_Total: 512 HugePages_Free: 512 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB The huge pages get partially allocate from ZONE_MOVABLE. Try unplugging 1G via virtio-mem (remember, all ZONE_MOVABLE). Inside the guest: [ 180.058992] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.060531] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.061972] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.063413] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.064838] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.065848] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.066794] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.067738] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.068669] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.069598] alloc_contig_range: [1bfc00, 1c0000) PFNs busy" Oscar Salvador (2): mm: Make alloc_contig_range handle free hugetlb pages mm: Make alloc_contig_range handle in-use hugetlb pages include/linux/hugetlb.h | 7 +++++ mm/compaction.c | 22 ++++++++++++++ mm/hugetlb.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++ mm/vmscan.c | 5 ++-- 4 files changed, 109 insertions(+), 2 deletions(-) -- 2.16.3
