Hi!
> High memory pressure can cause MemFree to temporarily drop below the
> min_free_kbytes threshold before the kernel reclaimer can catch up.
> This results in intermittent test failures, particularly observed on
> openQA aarch64 machines.
>
> Implement a 1-second grace period with exponential backoff polling
> (from 1ms up to 512ms) in check_monitor() to allow the kernel time to
> reclaim memory.
>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
> Signed-off-by: Wei Gao <wegao@suse.com>
> ---
> v1->v2:
> - Combine TINFO and TFAIL messages in check_monitor() for cleaner output.
> - Remove end = 0;
>
> .../kernel/mem/tunable/min_free_kbytes.c | 33 +++++++++++++------
> 1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c b/testcases/kernel/mem/tunable/min_free_kbytes.c
> index a62e4ae9d..e0342ef06 100644
> --- a/testcases/kernel/mem/tunable/min_free_kbytes.c
> +++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
> @@ -1,6 +1,6 @@
> // SPDX-License-Identifier: GPL-2.0-or-later
> /*
> - * Copyright (c) Linux Test Project, 2012-2025
> + * Copyright (c) Linux Test Project, 2012-2026
> * Copyright (C) 2012-2017 Red Hat, Inc.
> */
>
> @@ -140,14 +140,13 @@ static void test_tune(unsigned long overcommit_policy)
> } else {
> if (WIFEXITED(status)) {
> if (WEXITSTATUS(status) != 0) {
> - tst_res(TFAIL, "child unexpectedly "
> - "failed: %d", status);
> + tst_res(TFAIL, "child unexpectedly failed: %d",
> + status);
We do have tst_strstatus().
> }
> } else if (!WIFSIGNALED(status) ||
> WTERMSIG(status) != SIGKILL) {
> - tst_res(TFAIL,
> - "child unexpectedly failed: %d",
> - status);
> + tst_res(TFAIL, "child unexpectedly failed: %d",
> + status);
> }
> }
> }
> @@ -183,18 +182,32 @@ static void check_monitor(void)
> {
> unsigned long tune;
> unsigned long memfree;
> + int i;
>
> while (!end) {
> memfree = SAFE_READ_MEMINFO("MemFree:");
> tune = TST_SYS_CONF_LONG_GET(MIN_FREE_KBYTES);
>
> if (memfree < tune) {
> - tst_res(TINFO, "MemFree is %lu kB, "
> - "min_free_kbytes is %lu kB", memfree, tune);
> - tst_res(TFAIL, "MemFree < min_free_kbytes");
> + /*
> + * Give it some time to reclaim. The kernel should keep
> + * MemFree above min_free_kbytes, but transient drops
> + * are possible under high pressure.
> + */
> + for (i = 1; i < 1024; i *= 2) {
> + usleep(i * 1000);
> + memfree = SAFE_READ_MEMINFO("MemFree:");
> + if (memfree >= tune)
> + break;
> + }
> +
> + if (memfree < tune) {
> + tst_res(TFAIL, "MemFree %lu kB < min_free_kbytes %lu kB",
> + memfree, tune);
> + }
> }
Looks good.
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
I think that we also want to change the test so that the monitor is
started and stopped for each testcase with a specific value we set the
min_free_kbytes to. Running it asynchronously like this may mean that we
will be looking for a wrong value for the second if we are unlucky. But
that can be done later on.
--
Cyril Hrubis
chrubis@suse.cz