[PATCH v2 14/23] mm: allow specifying custom oom constraint for BPF triggers

Roman Gushchin
2025-10-27T23:22:33Z

Currently there is a hard-coded list of possible oom constraints:
NONE, CPUSET, MEMORY_POLICY & MEMCG. Add a new one: CONSTRAINT_BPF.
Also, add an ability to specify a custom constraint name
when calling bpf_out_of_memory(). If an empty string is passed
as an argument, CONSTRAINT_BPF is displayed.

The resulting output in dmesg will look like this:

[ 315.224875] kworker/u17:0 invoked oom-killer: gfp_mask=0x0(), order=0, oom_score_adj=0
oom_policy=default
[ 315.226532] CPU: 1 UID: 0 PID: 74 Comm: kworker/u17:0 Not tainted 6.16.0-00015-gf09eb0d6badc #102 PREEMPT(full)
[ 315.226534] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-5.fc42 04/01/2014
[ 315.226536] Workqueue: bpf_psi_wq bpf_psi_handle_event_fn
[ 315.226542] Call Trace:
[ 315.226545] <TASK>
[ 315.226548] dump_stack_lvl+0x4d/0x70
[ 315.226555] dump_header+0x59/0x1c6
[ 315.226561] oom_kill_process.cold+0x8/0xef
[ 315.226565] out_of_memory+0x111/0x5c0
[ 315.226577] bpf_out_of_memory+0x6f/0xd0
[ 315.226580] ? srso_alias_return_thunk+0x5/0xfbef5
[ 315.226589] bpf_prog_3018b0cf55d2c6bb_handle_psi_event+0x5d/0x76
[ 315.226594] bpf__bpf_psi_ops_handle_psi_event+0x47/0xa7
[ 315.226599] bpf_psi_handle_event_fn+0x63/0xb0
[ 315.226604] process_one_work+0x1fc/0x580
[ 315.226616] ? srso_alias_return_thunk+0x5/0xfbef5
[ 315.226624] worker_thread+0x1d9/0x3b0
[ 315.226629] ? __pfx_worker_thread+0x10/0x10
[ 315.226632] kthread+0x128/0x270
[ 315.226637] ? lock_release+0xd4/0x2d0
[ 315.226645] ? __pfx_kthread+0x10/0x10
[ 315.226649] ret_from_fork+0x81/0xd0
[ 315.226652] ? __pfx_kthread+0x10/0x10
[ 315.226655] ret_from_fork_asm+0x1a/0x30
[ 315.226667] </TASK>
[ 315.239745] memory: usage 42240kB, limit 9007199254740988kB, failcnt 0
[ 315.240231] swap: usage 0kB, limit 0kB, failcnt 0
[ 315.240585] Memory cgroup stats for /cgroup-test-work-dir673/oom_test/cg2:
[ 315.240603] anon 42897408
[ 315.241317] file 0
[ 315.241493] kernel 98304
...
[ 315.255946] Tasks state (memory values in pages):
[ 315.256292] [ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name
[ 315.257107] [ 675] 0 675 162013 10969 10712 257 0 155648 0 0 test_progs
[ 315.257927] oom-kill:constraint=CONSTRAINT_BPF_PSI_MEM,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/cgroup-test-work-dir673/oom_test/cg2,task_memcg=/cgroup-test-work-dir673/oom_test/cg2,task=test_progs,pid=675,uid=0
[ 315.259371] Memory cgroup out of memory: Killed process 675 (test_progs) total-vm:648052kB, anon-rss:42848kB, file-rss:1028kB, shmem-rss:0kB, UID:0 pgtables:152kB oom_score_adj:0

Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
---
include/linux/oom.h | 4 ++++
mm/oom_kill.c | 38 +++++++++++++++++++++++++++++---------
2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/include/linux/oom.h b/include/linux/oom.h
index 3cbdcd013274..704fc0e786c6 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -19,6 +19,7 @@ enum oom_constraint {
CONSTRAINT_CPUSET,
CONSTRAINT_MEMORY_POLICY,
CONSTRAINT_MEMCG,
+ CONSTRAINT_BPF,
};

enum bpf_oom_flags {
@@ -63,6 +64,9 @@ struct oom_control {

/* Policy name */
const char *bpf_policy_name;
+
+ /* BPF-specific constraint name */
+ const char *bpf_constraint;
#endif
};

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index d7fca4bf575b..72a346261c79 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -240,13 +240,6 @@ long oom_badness(struct task_struct *p, unsigned long totalpages)
return points;
}

-static const char * const oom_constraint_text[] = {
- [CONSTRAINT_NONE] = "CONSTRAINT_NONE",
- [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
- [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
- [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
-};
-
static const char *oom_policy_name(struct oom_control *oc)
{
#ifdef CONFIG_BPF_SYSCALL
@@ -256,6 +249,27 @@ static const char *oom_policy_name(struct oom_control *oc)
return "default";
}

+static const char *oom_constraint_text(struct oom_control *oc)
+{
+ switch (oc->constraint) {
+ case CONSTRAINT_NONE:
+ return "CONSTRAINT_NONE";
+ case CONSTRAINT_CPUSET:
+ return "CONSTRAINT_CPUSET";
+ case CONSTRAINT_MEMORY_POLICY:
+ return "CONSTRAINT_MEMORY_POLICY";
+ case CONSTRAINT_MEMCG:
+ return "CONSTRAINT_MEMCG";
+#ifdef CONFIG_BPF_SYSCALL
+ case CONSTRAINT_BPF:
+ return oc->bpf_constraint ? : "CONSTRAINT_BPF";
+#endif
+ default:
+ WARN_ON_ONCE(1);
+ return "";
+ }
+}
+
/*
* Determine the type of allocation constraint.
*/
@@ -267,6 +281,9 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
bool cpuset_limited = false;
int nid;

+ if (oc->constraint == CONSTRAINT_BPF)
+ return CONSTRAINT_BPF;
+
if (is_memcg_oom(oc)) {
oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
return CONSTRAINT_MEMCG;
@@ -458,7 +475,7 @@ static void dump_oom_victim(struct oom_control *oc, struct task_struct *victim)
{
/* one line summary of the oom killer context. */
pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
- oom_constraint_text[oc->constraint],
+ oom_constraint_text(oc),
nodemask_pr_args(oc->nodemask));
cpuset_print_current_mems_allowed();
mem_cgroup_print_oom_context(oc->memcg, victim);
@@ -1350,11 +1367,14 @@ __bpf_kfunc int bpf_oom_kill_process(struct oom_control *oc,
* Returns a negative value if an error occurred.
*/
__bpf_kfunc int bpf_out_of_memory(struct mem_cgroup *memcg__nullable,
- int order, u64 flags)
+ int order, u64 flags,
+ const char *constraint_text__nullable)
{
struct oom_control oc = {
.memcg = memcg__nullable,
.order = order,
+ .constraint = CONSTRAINT_BPF,
+ .bpf_constraint = constraint_text__nullable,
};
int ret;

--
2.51.0