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 rather than generous. 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, and the case has timed out in a full matrix run, reporting a failure for a collapse that was still going. Keep three seconds as the floor and add a second per 128M to collapse. A 2M PMD is unchanged. A 512M PMD gets 19 seconds, which is headroom over the observed tail rather than a measured requirement. The budget bounds how long a real failure takes to report, not how long a passing case waits: wait_for_scan() returns as soon as the collapse turns up. arm64/64K: khugepaged all:anon 21 pass/1 fail -> 22 pass/0 fail. x86-64 is unchanged. Assisted-by: Claude-Code:claude-opus-5 Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/khugepaged.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 51fc1f04d0a0..0f828bfee31f 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -602,8 +602,10 @@ 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; + /* Three seconds as a floor, plus a second per 128M to collapse */ + const unsigned long bytes = (unsigned long)nr_hpages * hpage_size; + int timeout = 6 + 2 * (bytes / (128UL << 20)); int full_scans; - int timeout = 6; /* 3 seconds */ /* Sanity check */ if (!ops->check_huge(p, len, 0, hpage_size)) -- 2.54.0
