Packet receive timeouts were traced to sparse HugeTLB unmapping in production. A task unmapping a sparse 2.5 TiB HugeTLB mapping could remain in kernel context for over 40 ms without reaching a scheduling point while walking empty huge PTEs. Although hard IRQs could still be handled, the per-CPU ksoftirqd thread and other runnable tasks could not run during that interval, delaying NET_RX softirq work queued to ksoftirqd. Add cond_resched() at the beginning of the hugepage loop so ksoftirqd and other runnable tasks can run between iterations. Testing with PREEMPT_NONE showed that the maximum interval between scheduling points fell from over 40 ms to below 2.5 ms. Total time spent in __unmap_hugepage_range() remained about 36 ms. Reported-by: Lance Yang Tested-by: Lance Yang Signed-off-by: Leon Hwang --- mm/hugetlb.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index dded1768193a..0a91aac2369f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5233,6 +5233,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, last_addr_mask = hugetlb_mask_last_page(h); address = start; for (; address < end; address += sz) { + cond_resched(); + ptep = hugetlb_walk(vma, address, sz); if (!ptep) { address |= last_addr_mask; -- 2.55.0