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From: Shakeel Butt To: Peilin Ye Cc: Alexei Starovoitov , Johannes Weiner , Tejun Heo , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Kumar Kartikeya Dwivedi , Josh Don , Barret Rhoden , linux-mm@kvack.org Subject: Re: [PATCH bpf] bpf/helpers: Skip memcg accounting in __bpf_async_init() Message-ID: References: <20250905061919.439648-1-yepeilin@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: n8wia1x16icxyaxb3fjnx8iuzu7e8dad X-Rspam-User: X-Rspamd-Queue-Id: ADC45C000A X-Rspamd-Server: rspam01 X-HE-Tag: 1757104366-455289 X-HE-Meta: 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 udZWGohT pvY0Ac5u00I0zK0caeZzfKOwdDuYPIixx6dwMqDSI2p6ztxwbkorS+AMO94yQ1eqQcNtNLHrLTpP+SoZv9Ey5ApBx3IhDVEoWYam3djp99XA3be8Gn2GQD23aUJt/kTM5kKcrKx746HW6aQBt36Wy/loj/MNpZY2Goh3dPCLKqkATAXUJ9XZV5ygYqTUC6gpmKGTz/UP5wCVUuffQTMgJ4MBQFlhvs+D1DsETQKG3VrLj06JffKdJTMzvwWytpu10Fi68W2Nz/JJUOjwvPzjqR6gnzuUmuABzYnyNvndQxMWm33u/ymvVDdEaMx8fH6/aWkQoJBKamXFB4ZUMzUd3L5FgjAIXDUcWYrHhlrrIMNiS+6v040hKinRu32zLr28M/F3i X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 05, 2025 at 07:14:57PM +0000, Peilin Ye wrote: > 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 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. Trylock approach will not work as there are multiple locks in this codepath. Better to use __GFP_HIGH instead of GFP_ATOMIC in __bpf_async_init().