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Tue, 11 Aug 2026 04:48:27 -0700 (PDT) Received: from bj-kjy-standalone-gaoxiang17.mioffice.cn ([43.224.245.230]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-392ee1e369esm1850103a91.2.2026.08.11.04.48.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Aug 2026 04:48:27 -0700 (PDT) From: Xiang Gao X-Google-Original-From: Xiang Gao To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , Lorenzo Stoakes , gao xu , yinchuang1@xiaomi.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Xiang Gao Subject: [RFC] tracing: aggregate ring-buffer usage statistics Date: Tue, 11 Aug 2026 19:48:18 +0800 Message-Id: <20260811114818.1449933-1-gaoxiang17@xiaomi.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, I would like to clarify the motivation for a tracing-specific memory usage interface. The original requirement comes from Android lost-RAM attribution. Ftrace ring-buffer data pages are not represented as a separate memory category, so userspace memory diagnostics may treat them as lost RAM. The memory can be spread across the global trace array, dynamically created tracing instances, and snapshot buffers. Userspace can read buffer_total_size_kb for the global trace array and each instance, but it has to discover and sum all instances, and snapshot buffer capacity is not exposed through the same per-instance total. On one Android device, the global buffer and 24 tracing instances accounted for 395,664 kB of ring-buffer data capacity. This makes the missing attribution significant for low-memory diagnostics. The core requirement is a stable tracing-specific interface that allows userspace to obtain the aggregate tracing buffer usage without walking all instances. It does not need to be part of /proc/meminfo or show_mem(). One possible interface would be under: /sys/kernel/tracing/trace_stats/ It could provide an aggregate buffer value together with a breakdown for main and snapshot buffers. Per-CPU statistics could also be added if useful. Thanks, Xiang