From: Peilin Ye <yepeilin@google.com>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Josh Don <joshdon@google.com>, Barret Rhoden <brho@google.com>,
linux-mm@kvack.org
Subject: Re: [PATCH bpf] bpf/helpers: Skip memcg accounting in __bpf_async_init()
Date: Fri, 5 Sep 2025 19:14:57 +0000 [thread overview]
Message-ID: <aLs2sV72B98i3i1Q@google.com> (raw)
In-Reply-To: <qwrl5ivlaou2qqbrj4wh2vi4uqmeny2zyfidkjizkyyzta3uo3@z6bjemb7om6y>
On Fri, Sep 05, 2025 at 10:31:07AM -0700, Shakeel Butt wrote:
> On Fri, Sep 05, 2025 at 08:18:25AM -0700, Alexei Starovoitov wrote:
> > On Thu, Sep 4, 2025 at 11:20 PM Peilin Ye <yepeilin@google.com> wrote:
> > > As pointed out by Kumar, we can use bpf_mem_alloc() and friends for
> > > bpf_hrtimer and bpf_work, to skip memcg accounting.
> >
> > This is a short term workaround that we shouldn't take.
> > Long term bpf_mem_alloc() will use kmalloc_nolock() and
> > memcg accounting that was already made to work from any context
> > except that the path of memcg_memory_event() wasn't converted.
> >
> > Shakeel,
> >
> > Any suggestions how memcg_memory_event()->cgroup_file_notify()
> > can be fixed?
> > Can we just trylock and skip the event?
>
> Will !gfpflags_allow_spinning(gfp_mask) be able to detect such call
> chains? If yes, then we can change memcg_memory_event() to skip calls to
> cgroup_file_notify() if spinning is not allowed.
I tried the below diff, but unfortunately __bpf_async_init() calls
bpf_map_kmalloc_node() with GFP_ATOMIC, so gfpflags_allow_spinning()
would return true. I'll try the trylock-and-skip approach.
Thanks,
Peilin Ye
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2350,11 +2350,12 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (unlikely(task_in_memcg_oom(current)))
goto nomem;
- if (!gfpflags_allow_blocking(gfp_mask))
+ if (!gfpflags_allow_blocking(gfp_mask)) {
goto nomem;
-
- memcg_memory_event(mem_over_limit, MEMCG_MAX);
- raised_max_event = true;
+ } else if (gfpflags_allow_spinning(gfp_mask)) {
+ memcg_memory_event(mem_over_limit, MEMCG_MAX);
+ raised_max_event = true;
+ }
psi_memstall_enter(&pflags);
nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
@@ -2419,7 +2420,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
* If the allocation has to be enforced, don't forget to raise
* a MEMCG_MAX event.
*/
- if (!raised_max_event)
+ if (!raised_max_event && gfpflags_allow_spinning(gfp_mask))
memcg_memory_event(mem_over_limit, MEMCG_MAX);
/*
next prev parent reply other threads:[~2025-09-05 19:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20250905061919.439648-1-yepeilin@google.com>
[not found] ` <CAADnVQKAd-jubdQ9ja=xhTqahs+2bk2a+8VUTj1bnLpueow0Lg@mail.gmail.com>
2025-09-05 17:31 ` Shakeel Butt
2025-09-05 18:23 ` Peilin Ye
2025-09-05 19:14 ` Peilin Ye [this message]
2025-09-05 20:32 ` Shakeel Butt
2025-09-05 19:48 ` Shakeel Butt
2025-09-05 20:31 ` Peilin Ye
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