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[104.155.91.135]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48862795215sm3484729f8f.37.2026.09.22.02.42.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Sep 2026 02:42:46 -0700 (PDT) Date: Tue, 22 Sep 2026 10:42:43 +0100 From: Vincent Donnefort To: Xiang Gao Cc: Steven Rostedt , Donggeun Yoo , 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: Re: [PATCH v4 2/2] tracing: add per-CPU memory usage statistics in tracefs Message-ID: References: <20260916063322.472172-1-gaoxiang17@xiaomi.com> <20260921113047.1152602-1-gaoxiang17@xiaomi.com> <20260921113047.1152602-3-gaoxiang17@xiaomi.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260921113047.1152602-3-gaoxiang17@xiaomi.com> On Mon, Sep 21, 2026 at 07:30:46PM +0800, Xiang Gao wrote: > 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: Could you split the documentation part into a different commit? > > 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 > -- Vincent