From: "Kiryl Shutsemau (Meta)" <[email protected]> wait_for_scan() gives every case the same three seconds, whatever the huge page costs to build. collapse_full() asks for four of them: 8M at a 2M PMD, but 2G at a 512M PMD -- arm64 with 64K base pages. Three seconds is thin at that size, and the case has reported a failure for a collapse that was still going.
The timeout is a ceiling on a poll loop, not a sleep: the loop stops as soon as ops->check_huge() sees the collapse, or as soon as full_scans has advanced by two. Raising it costs a passing case nothing. Across 80 runs of collapse_full() on arm64 with 64K pages the wait was half a second in 73 of them, with a tail to two seconds. Keep three seconds as the floor and add a second per 128M collapsed. A 2M PMD is unchanged, so x86-64 is too; a 512M PMD gets 19 seconds. On arm64 with 64K pages a passing ./khugepaged all:anon takes 49 seconds under TCG before and after this change. Assisted-by: LLM Acked-by: Lorenzo Stoakes (ARM) <[email protected]> Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> Tested-by: Muhammad Usama Anjum <[email protected]> Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/khugepaged.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 1ca7c6978571..48e0040d53b4 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -556,8 +556,11 @@ static bool wait_for_scan(const char *msg, char *p, size_t len, int nr_hpages, int collap_order, struct mem_ops *ops) { unsigned long hpage_size = page_size << collap_order; - int full_scans; - int timeout = 6; /* 3 seconds */ + unsigned long bytes = (unsigned long)nr_hpages * hpage_size; + int timeout, full_scans; + + /* Half-second ticks: three seconds floor, plus a second per 128M */ + timeout = 6 + 2 * (bytes / (128UL << 20)); /* Sanity check */ if (!ops->check_huge(p, len, 0, hpage_size)) -- 2.54.0
