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Message-ID: <CALC8CXfcJjoHyZAiHm1meGtKf9CAbgnmhy4fxMqaa5Gb_ZHvwQ@mail.gmail.com>
Date: Thu, 2 Oct 2025 12:37:25 -0400
From: ChaosEsque Team <chaosesqueteam@...il.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: linux-mm@...ck.org, bpf@...r.kernel.org,
Suren Baghdasaryan <surenb@...gle.com>, Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...e.com>,
David Rientjes <rientjes@...gle.com>, Matt Bobrowski <mattbobrowski@...gle.com>,
Song Liu <song@...nel.org>, Kumar Kartikeya Dwivedi <memxor@...il.com>, Alexei Starovoitov <ast@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 07/14] mm: allow specifying custom oom constraint for
bpf triggers
Roman Gushchin...
RUSSKIEEEEEE
On Mon, Aug 18, 2025 at 1:05 PM Roman Gushchin <roman.gushchin@...ux.dev> wrote:
>
> 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@...ux.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 ef453309b7ea..4b04944b42de 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,
> };
>
> /*
> @@ -58,6 +59,9 @@ 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 df409f0fac45..67afcd43a5f7 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);
> @@ -1344,11 +1361,14 @@ __bpf_kfunc int bpf_oom_kill_process(struct oom_control *oc,
> * Returns a negative value if an error has been occurred.
> */
> __bpf_kfunc int bpf_out_of_memory(struct mem_cgroup *memcg__nullable,
> - int order, bool wait_on_oom_lock)
> + int order, bool wait_on_oom_lock,
> + const char *constraint_text__nullable)
> {
> struct oom_control oc = {
> .memcg = memcg__nullable,
> .order = order,
> + .constraint = CONSTRAINT_BPF,
> + .bpf_constraint = constraint_text__nullable,
> };
> int ret;
>
> --
> 2.50.1
>
>
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