TLDR: If a mempolicy is in effect(oc->constraint == CONSTRAINT_MEMORY_POLICY), out_of_memory() will select victim on specific node to kill. So that kernel can avoid accidental killing on NUMA system. Problem: Before this patch series, oom will only kill the process with the highest memory usage. by selecting process with the highest oom_badness on the entire system to kill. This works fine on UMA system, but may have some accidental killing on NUMA system. As shown below, if process c.out is bind to Node1 and keep allocating pages from Node1, a.out will be killed first. But killing a.out did't free any mem on Node1, so c.out will be killed then. A lot of our AMD machines have 8 numa nodes. In these systems, there is a greater chance of triggering this problem. OOM before patches: ``` Per-node process memory usage (in MBs) PID Node 0 Node 1 Total ----------- ---------- ------------- ---------- 3095 a.out 3073.34 0.11 3073.45(Killed first. Maximum memory consumption) 3199 b.out 501.35 1500.00 2001.35 3805 c.out 1.52 (grow)2248.00 2249.52(Killed then. Node1 is full) ----------- ---------- ------------- ---------- Total 3576.21 3748.11 7324.31 ``` Solution: We store per node rss in mm_rss_stat for each process. If a page allocation with mempolicy in effect(oc->constraint == CONSTRAINT_MEMORY_POLICY) triger oom. We will calculate oom_badness with rss counter for the corresponding node. Then select the process with the highest oom_badness on the corresponding node to kill. OOM after patches: ``` Per-node process memory usage (in MBs) PID Node 0 Node 1 Total ----------- ---------- ------------- ---------- 3095 a.out 3073.34 0.11 3073.45 3199 b.out 501.35 1500.00 2001.35 3805 c.out 1.52 (grow)2248.00 2249.52(killed) ----------- ---------- ------------- ---------- Total 3576.21 3748.11 7324.31 ``` Gang Li (5): mm: add a new parameter `node` to `get/add/inc/dec_mm_counter` mm: add numa_count field for rss_stat mm: add numa fields for tracepoint rss_stat mm: enable per numa node rss_stat count mm, oom: enable per numa node oom for CONSTRAINT_MEMORY_POLICY arch/s390/mm/pgtable.c | 4 +- fs/exec.c | 2 +- fs/proc/base.c | 6 +- fs/proc/task_mmu.c | 14 ++-- include/linux/mm.h | 59 ++++++++++++----- include/linux/mm_types_task.h | 16 +++++ include/linux/oom.h | 2 +- include/trace/events/kmem.h | 27 ++++++-- kernel/events/uprobes.c | 6 +- kernel/fork.c | 70 +++++++++++++++++++- mm/huge_memory.c | 13 ++-- mm/khugepaged.c | 4 +- mm/ksm.c | 2 +- mm/madvise.c | 2 +- mm/memory.c | 116 ++++++++++++++++++++++++---------- mm/migrate.c | 2 + mm/migrate_device.c | 2 +- mm/oom_kill.c | 59 ++++++++++++----- mm/rmap.c | 16 ++--- mm/swapfile.c | 4 +- mm/userfaultfd.c | 2 +- 21 files changed, 317 insertions(+), 111 deletions(-) -- 2.20.1
