On 9/8/26 8:50 PM, Kiryl Shutsemau wrote:
From: "Kiryl Shutsemau (Meta)" <[email protected]> collapse_swapin_single_pte() and collapse_max_ptes_swap() swap a range out and then require smaps to report exactly the count they asked for. Two things keep that count from arriving. MADV_PAGEOUT is best effort, so the count often turns up a moment late. And wait_for_scan() leaves the range eligible for collapsing, so khugepaged is still working on it. Collapsing reads the swapped-out pages back in, so the daemon empties the swap as fast as the case fills it. On arm64 with 64K pages max_ptes_swap is 1024 pages, which is 64M a step, and the case loses the race: # Swapout 1024 of 8192 pages... Fail not ok 10 collapse_max_ptes_swap Retry for up to two seconds, holding the range out of khugepaged's reach meanwhile. The collapse each case runs next restores MADV_HUGEPAGE, so only the setup is affected. If the pages still won't swap out, skip: no swap, swap too small or full, a memcg cap or busy writeback. None of that is a kernel bug. Assisted-by: LLM Reviewed-by: Muhammad Usama Anjum <[email protected]> Tested-by: Muhammad Usama Anjum <[email protected]> Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> ---
Make sense to me. So Reviewed-by: Baolin Wang <[email protected]>
