test_swapin_nozswap can hit OOM before reaching its assertions on some
setups. The test currently sets memory.max=8M and then allocates/reads
32M with memory.zswap.max=0, which may over-constrain reclaim and kill
the workload process.
Replace hardcoded sizes with PAGE_SIZE-based values:
- control_allocation_size = PAGE_SIZE * 512
- memory.max = control_allocation_size * 3 / 4
- minimum expected swap = control_allocation_size / 4
This keeps the test pressure model intact (allocate/read beyond memory.max to
force swap-in/out) while making it more robust across different environments.
The test intent is unchanged: confirm that swapping occurs while zswap remains
unused when memory.zswap.max=0.
=== Error Logs ===
# ./test_zswap
TAP version 13
1..7
ok 1 test_zswap_usage
not ok 2 test_swapin_nozswap
...
# dmesg
[271641.879153] test_zswap invoked oom-killer: gfp_mask=0xcc0(GFP_KERNEL),
order=0, oom_score_adj=0
[271641.879168] CPU: 1 UID: 0 PID: 177372 Comm: test_zswap Kdump: loaded Not
tainted 6.12.0-211.el10.ppc64le #1 VOLUNTARY
[271641.879171] Hardware name: IBM,9009-41A POWER9 (architected) 0x4e0202
0xf000005 of:IBM,FW940.02 (UL940_041) hv:phyp pSeries
[271641.879173] Call Trace:
[271641.879174] [c00000037540f730] [c00000000127ec44]
dump_stack_lvl+0x88/0xc4 (unreliable)
[271641.879184] [c00000037540f760] [c0000000005cc594] dump_header+0x5c/0x1e4
[271641.879188] [c00000037540f7e0] [c0000000005cb464]
oom_kill_process+0x324/0x3b0
[271641.879192] [c00000037540f860] [c0000000005cbe48]
out_of_memory+0x118/0x420
[271641.879196] [c00000037540f8f0] [c00000000070d8ec]
mem_cgroup_out_of_memory+0x18c/0x1b0
[271641.879200] [c00000037540f990] [c000000000713888]
try_charge_memcg+0x598/0x890
[271641.879204] [c00000037540fa70] [c000000000713dbc] charge_memcg+0x5c/0x110
[271641.879207] [c00000037540faa0] [c0000000007159f8]
__mem_cgroup_charge+0x48/0x120
[271641.879211] [c00000037540fae0] [c000000000641914]
alloc_anon_folio+0x2b4/0x5a0
[271641.879215] [c00000037540fb60] [c000000000641d58]
do_anonymous_page+0x158/0x6b0
[271641.879218] [c00000037540fbd0] [c000000000642f8c]
__handle_mm_fault+0x4bc/0x910
[271641.879221] [c00000037540fcf0] [c000000000643500]
handle_mm_fault+0x120/0x3c0
[271641.879224] [c00000037540fd40] [c00000000014bba0]
___do_page_fault+0x1c0/0x980
[271641.879228] [c00000037540fdf0] [c00000000014c44c]
hash__do_page_fault+0x2c/0xc0
[271641.879232] [c00000037540fe20] [c0000000001565d8]
do_hash_fault+0x128/0x1d0
[271641.879236] [c00000037540fe50] [c000000000008be0]
data_access_common_virt+0x210/0x220
[271641.879548] Tasks state (memory values in pages):
...
[271641.879550] [ pid ] uid tgid total_vm rss rss_anon rss_file
rss_shmem pgtables_bytes swapents oom_score_adj name
[271641.879555] [ 177372] 0 177372 571 0 0 0
0 51200 96 0 test_zswap
[271641.879562]
oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/no_zswap_test,task_memcg=/no_zswap_test,task=test_zswap,pid=177372,uid=0
[271641.879578] Memory cgroup out of memory: Killed process 177372
(test_zswap) total-vm:36544kB, anon-rss:0kB, file-rss:0kB, shmem-rss:0kB, UID:0
pgtables:50kB oom_score_adj:0
Signed-off-by: Li Wang <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Acked-by: Yosry Ahmed <[email protected]>
---
Notes:
v3:
- Replace fixed 8M/32M sizing with PAGE_SIZE-based sizing in
test_swapin_nozswap.
- Set memory.max to 3/4 of workload size to reduce OOM risk while still
forcing reclaim/swap activity.
- Derive minimum swap expectation from workload size (1/4) instead of a
fixed 8M threshold.
v2:
- No change.
tools/testing/selftests/cgroup/test_zswap.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/cgroup/test_zswap.c
b/tools/testing/selftests/cgroup/test_zswap.c
index e69d845d3592..04796b6641b8 100644
--- a/tools/testing/selftests/cgroup/test_zswap.c
+++ b/tools/testing/selftests/cgroup/test_zswap.c
@@ -160,21 +160,25 @@ static int test_zswap_usage(const char *root)
static int test_swapin_nozswap(const char *root)
{
int ret = KSFT_FAIL;
- char *test_group;
- long swap_peak, zswpout;
+ char *test_group, mem_max_buf[32];
+ long swap_peak, zswpout, min_swap;
+ size_t control_allocation_size = sysconf(_SC_PAGESIZE) * 512;
+
+ min_swap = control_allocation_size / 4;
+ snprintf(mem_max_buf, sizeof(mem_max_buf), "%zu",
control_allocation_size * 3/4);
test_group = cg_name(root, "no_zswap_test");
if (!test_group)
goto out;
if (cg_create(test_group))
goto out;
- if (cg_write(test_group, "memory.max", "8M"))
+ if (cg_write(test_group, "memory.max", mem_max_buf))
goto out;
if (cg_write(test_group, "memory.zswap.max", "0"))
goto out;
/* Allocate and read more than memory.max to trigger swapin */
- if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
+ if (cg_run(test_group, allocate_and_read_bytes, (void
*)control_allocation_size))
goto out;
/* Verify that pages are swapped out, but no zswap happened */
@@ -184,8 +188,9 @@ static int test_swapin_nozswap(const char *root)
goto out;
}
- if (swap_peak < MB(24)) {
- ksft_print_msg("at least 24MB of memory should be swapped
out\n");
+ if (swap_peak < min_swap) {
+ ksft_print_msg("at least %ldMB of memory should be swapped
out\n",
+ min_swap / MB(1));
goto out;
}
--
2.53.0
