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Mon, 21 Sep 2026 04:31:04 -0700 (PDT) From: Xiang Gao X-Google-Original-From: Xiang Gao To: Steven Rostedt , Vincent Donnefort , Donggeun Yoo Cc: Masami Hiramatsu , Mathieu Desnoyers , Lorenzo Stoakes , gao xu , yinchuang1@xiaomi.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Xiang Gao Subject: [PATCH v4 2/2] tracing: add per-CPU memory usage statistics in tracefs Date: Mon, 21 Sep 2026 19:30:46 +0800 Message-Id: <20260921113047.1152602-3-gaoxiang17@xiaomi.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260921113047.1152602-1-gaoxiang17@xiaomi.com> References: <20260916063322.472172-1-gaoxiang17@xiaomi.com> <20260921113047.1152602-1-gaoxiang17@xiaomi.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Provide a per-CPU view of the tracing ring-buffer memory usage under trace_stats/per_cpu/cpuN/memory_usage_kb, using the same format as the aggregate file. Each file reports only the buffers belonging to that CPU across the global trace array and all tracing instances. Signed-off-by: Xiang Gao --- Documentation/trace/ftrace.rst | 3 ++ kernel/trace/trace.c | 67 +++++++++++++++++++++++++++++++++- 2 files changed, 69 insertions(+), 1 deletion(-) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 99ddfe26b7cd..e53cdd8d6702 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -230,6 +230,9 @@ of ftrace. Here is a list of some of the key files: buffers: ... snapshot_buffers: ... + The same file is provided under trace_stats/per_cpu/cpuN/, reporting + only the buffers belonging to that CPU. + buffer_subbuf_size_kb: This sets or displays the sub buffer size. The ring buffer is broken up diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d4a913ff8a69..4010f28f3ebf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5844,6 +5844,52 @@ static const struct file_operations trace_mem_fops = { .release = single_release, }; +static struct trace_mem_stats trace_buffers_memory_cpu(int cpu) +{ + struct trace_mem_stats stats = {}; + struct trace_array *tr; + + guard(mutex)(&trace_types_lock); + + list_for_each_entry(tr, &ftrace_trace_arrays, list) + trace_array_buffer_memory(tr, cpu, &stats.buffers, + &stats.snapshot); + + /* Account for the bootstrapping temp_buffer as well. */ + if (temp_buffer) + stats.buffers += ring_buffer_memory_size(temp_buffer, cpu); + + return stats; +} + +static int trace_mem_per_cpu_show(struct seq_file *m, void *v) +{ + struct trace_mem_stats stats = trace_buffers_memory_cpu((long)m->private); + + seq_printf(m, "buffers: %lu\n", stats.buffers >> 10); + seq_printf(m, "snapshot_buffers: %lu\n", stats.snapshot >> 10); + + return 0; +} + +static int trace_mem_per_cpu_open(struct inode *inode, struct file *file) +{ + int ret; + + ret = tracing_check_open_get_tr(NULL); + if (ret) + return ret; + + return single_open(file, trace_mem_per_cpu_show, inode->i_private); +} + +static const struct file_operations trace_mem_per_cpu_fops = { + .open = trace_mem_per_cpu_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + #define LAST_BOOT_HEADER ((void *)1) static void *l_next(struct seq_file *m, void *v, loff_t *pos) @@ -9360,7 +9406,9 @@ static struct notifier_block trace_module_nb = { static __init void init_trace_stats_tracefs(void) { - struct dentry *stats_dir; + struct dentry *stats_dir, *per_cpu_dir, *cpu_dir; + char cpu_dir_name[30]; + int cpu; /* * tracer_alloc_buffers() frees tracing_buffer_mask and temp_buffer @@ -9376,6 +9424,23 @@ static __init void init_trace_stats_tracefs(void) trace_create_file("memory_usage_kb", TRACE_MODE_READ, stats_dir, NULL, &trace_mem_fops); + + per_cpu_dir = tracefs_create_dir("per_cpu", stats_dir); + if (!per_cpu_dir) + return; + + for_each_tracing_cpu(cpu) { + snprintf(cpu_dir_name, 30, "cpu%d", cpu); + cpu_dir = tracefs_create_dir(cpu_dir_name, per_cpu_dir); + if (!cpu_dir) { + pr_warn("Could not create tracefs '%s' entry\n", + cpu_dir_name); + continue; + } + + trace_create_file("memory_usage_kb", TRACE_MODE_READ, cpu_dir, + (void *)(long)cpu, &trace_mem_per_cpu_fops); + } } static __init void tracer_init_tracefs_work_func(struct work_struct *work) -- 2.34.1