For regular processes, the time taken in its exit() path to free its used memory is not a problem. But there are heavy ones that consume several Terabytes memory and the time taken to free its memory could last more than ten minutes. To optimize this use case, a parallel free method is proposed here. For detailed explanation, please refer to patch 2/5. I'm not sure if we need patch 4/5 which can avoid page accumulation being interrupted in some case(patch description has more information). My test case, which only deal with anon memory doesn't get any help out of this of course. It can be safely dropped if it is deemed not useful. A test program that did a single malloc() of 320G memory is used to see how useful the proposed parallel free solution is, the time calculated is for the free() call. Test machine is a Haswell EX which has 4nodes/72cores/144threads with 512G memory. All tests are done with THP disabled. kernel time v4.10 10.8s ±2.8% this patch(with default setting) 5.795s ±5.8% Patch 3/5 introduced a dedicated workqueue for the free workers and here are more results when setting different values for max_active of this workqueue: max_active: time 1 8.9s ±0.5% 2 5.65s ±5.5% 4 4.84s ±0.16% 8 4.77s ±0.97% 16 4.85s ±0.77% 32 6.21s ±0.46% Comments are welcome. Aaron Lu (5): mm: add tlb_flush_mmu_free_batches mm: parallel free pages mm: use a dedicated workqueue for the free workers mm: add force_free_pages in zap_pte_range mm: add debugfs interface for parallel free tuning include/asm-generic/tlb.h | 12 ++-- mm/memory.c | 138 +++++++++++++++++++++++++++++++++++++++------- 2 files changed, 122 insertions(+), 28 deletions(-) -- 2.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
