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[34.34.182.0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-498365cd06fsm11724877f8f.40.2026.11.11.08.47.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 08:47:41 -0800 (PST) Date: Wed, 11 Nov 2026 16:47:38 +0000 From: Vincent Donnefort To: Tao Cui Cc: akpm@linux-foundation.org, dgilbert@interlog.com, mkp@kernel.org, loberman@redhat.com, jmeneghi@redhat.com, kraxel@redhat.com, vivek.kasireddy@intel.com, mst@redhat.com, jasowangio@gmail.com, eperezma@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, jgg@ziepe.ca, kevin.tian@intel.com, axboe@kernel.dk, linux-mm@kvack.org, James.Bottomley@hansenpartnership.com, sumit.semwal@linaro.org, christian.koenig@amd.com, phasta@kernel.org, joro@8bytes.org, will@kernel.org, linux-scsi@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-trace-kernel@vger.kernel.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, bobbyeshleman@meta.com, mathieu.desnoyers@efficios.com, robin.murphy@arm.com, mason@kernel.org, aesteve@redhat.com, tjmercier@google.com, harry@kernel.org, vbabka@suse.cz, cuitao@kylinos.cn Subject: Re: [PATCH 4/7] tracing: account ring buffer pages and trace_array metadata to memcg Message-ID: References: <20261106131829.3228926-1-cui.tao@linux.dev> <20261106131829.3228926-5-cui.tao@linux.dev> X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261106131829.3228926-5-cui.tao@linux.dev> On Fri, Nov 06, 2026 at 09:18:26PM +0800, Tao Cui wrote: > From: Tao Cui > > Creating an instance immediately allocates two full sets of per-cpu > ring buffers, array buffer plus snapshot, about 1.375MB per cpu per set > on the default config, plus the trace_array and its name. None of it > is charged: neither trace.c nor ring_buffer.c passes __GFP_ACCOUNT, > while user_events in the same directory accounts everything it > allocates. > > Instance creation is currently gated by tracefs file permissions > alone, so a > rootful container with the host tracefs bound in can create instances > until the host runs out of memory. Charge the ring buffer pages and > the trace_array metadata to the creating cgroup. > > Signed-off-by: Tao Cui > --- > kernel/trace/ring_buffer.c | 8 +++++++- > kernel/trace/trace.c | 6 +++--- > 2 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 1fd28a72e6ee..676c059c112c 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -441,7 +441,13 @@ static struct buffer_data_page *alloc_cpu_data(int cpu, int order) > * gracefully without invoking oom-killer and the system is not > * destabilized. > */ > - mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_COMP | __GFP_ZERO; > + /* > + * The subbuffers are charged to the memcg of whoever caused the > + * allocation: the creator of a trace instance, or root at boot for > + * the global trace. > + */ > + mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_COMP | __GFP_ZERO | > + __GFP_ACCOUNT; > > page = alloc_pages_node(cpu_to_node(cpu), mflags, order); > if (!page) Hum, by default tracefs is root only. And even if made accessible to other users: 1. The life span of a trace instance is not tied to the caller. 2. The ring buffer is shared by multiple users. Overall I am not convinced charging the creator makes much sense. Eventually a few allocations for iterators could be GFP_ACCOUNT. -- Vincent > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index e8c4efa8107b..04b60b9cc4f5 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -8693,11 +8693,11 @@ trace_array_create_systems(const char *name, const char *systems, > int ret; > > ret = -ENOMEM; > - tr = kzalloc_obj(*tr); > + tr = kzalloc_obj(*tr, GFP_KERNEL_ACCOUNT); > if (!tr) > return ERR_PTR(ret); > > - tr->name = kstrdup(name, GFP_KERNEL); > + tr->name = kstrdup(name, GFP_KERNEL_ACCOUNT); > if (!tr->name) > goto out_free_tr; > > @@ -8708,7 +8708,7 @@ trace_array_create_systems(const char *name, const char *systems, > goto out_free_tr; > > if (systems) { > - tr->system_names = kstrdup_const(systems, GFP_KERNEL); > + tr->system_names = kstrdup_const(systems, GFP_KERNEL_ACCOUNT); > if (!tr->system_names) > goto out_free_tr; > } > -- > 2.43.0 >