ring-buffer: Add per_cpu ring buffer control files

Add a debugfs entry under per_cpu/ folder for each cpu called
buffer_size_kb to control the ring buffer size for each CPU
independently.

If the global file buffer_size_kb is used to set size, the individual
ring buffers will be adjusted to the given size. The buffer_size_kb will
report the common size to maintain backward compatibility.

If the buffer_size_kb file under the per_cpu/ directory is used to
change buffer size for a specific CPU, only the size of the respective
ring buffer is updated. When tracing/buffer_size_kb is read, it reports
'X' to indicate that sizes of per_cpu ring buffers are not equivalent.

Link: http://lkml.kernel.org/r/1328212844-11889-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Justin Teravest <teravest@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 152 insertions, 38 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bbcde546f9f7..f11a285ee5bb 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -838,7 +838,8 @@ __acquires(kernel_lock)
 
                 /* If we expanded the buffers, make sure the max is expanded too */
                 if (ring_buffer_expanded && type->use_max_tr)
-                        ring_buffer_resize(max_tr.buffer, trace_buf_size);
+                        ring_buffer_resize(max_tr.buffer, trace_buf_size,
+                                                RING_BUFFER_ALL_CPUS);
 
                 /* the test is responsible for initializing and enabling */
                 pr_info("Testing tracer %s: ", type->name);
@@ -854,7 +855,8 @@ __acquires(kernel_lock)
 
                 /* Shrink the max buffer again */
                 if (ring_buffer_expanded && type->use_max_tr)
-                        ring_buffer_resize(max_tr.buffer, 1);
+                        ring_buffer_resize(max_tr.buffer, 1,
+                                                RING_BUFFER_ALL_CPUS);
 
                 printk(KERN_CONT "PASSED\n");
         }
@@ -3053,7 +3055,14 @@ int tracer_init(struct tracer *t, struct trace_array *tr)
         return t->init(tr);
 }
 
-static int __tracing_resize_ring_buffer(unsigned long size)
+static void set_buffer_entries(struct trace_array *tr, unsigned long val)
+{
+        int cpu;
+        for_each_tracing_cpu(cpu)
+                tr->data[cpu]->entries = val;
+}
+
+static int __tracing_resize_ring_buffer(unsigned long size, int cpu)
 {
         int ret;
 
@@ -3064,19 +3073,32 @@ static int __tracing_resize_ring_buffer(unsigned long size)
          */
         ring_buffer_expanded = 1;
 
-        ret = ring_buffer_resize(global_trace.buffer, size);
+        ret = ring_buffer_resize(global_trace.buffer, size, cpu);
         if (ret < 0)
                 return ret;
 
         if (!current_trace->use_max_tr)
                 goto out;
 
-        ret = ring_buffer_resize(max_tr.buffer, size);
+        ret = ring_buffer_resize(max_tr.buffer, size, cpu);
         if (ret < 0) {
-                int r;
+                int r = 0;
+
+                if (cpu == RING_BUFFER_ALL_CPUS) {
+                        int i;
+                        for_each_tracing_cpu(i) {
+                                r = ring_buffer_resize(global_trace.buffer,
+                                                global_trace.data[i]->entries,
+                                                i);
+                                if (r < 0)
+                                        break;
+                        }
+                } else {
+                        r = ring_buffer_resize(global_trace.buffer,
+                                                global_trace.data[cpu]->entries,
+                                                cpu);
+                }
 
-                r = ring_buffer_resize(global_trace.buffer,
-                                       global_trace.entries);
                 if (r < 0) {
                         /*
                          * AARGH! We are left with different
@@ -3098,14 +3120,21 @@ static int __tracing_resize_ring_buffer(unsigned long size)
                 return ret;
         }
 
-        max_tr.entries = size;
+        if (cpu == RING_BUFFER_ALL_CPUS)
+                set_buffer_entries(&max_tr, size);
+        else
+                max_tr.data[cpu]->entries = size;
+
  out:
-        global_trace.entries = size;
+        if (cpu == RING_BUFFER_ALL_CPUS)
+                set_buffer_entries(&global_trace, size);
+        else
+                global_trace.data[cpu]->entries = size;
 
         return ret;
 }
 
-static ssize_t tracing_resize_ring_buffer(unsigned long size)
+static ssize_t tracing_resize_ring_buffer(unsigned long size, int cpu_id)
 {
         int cpu, ret = size;
 
@@ -3121,12 +3150,19 @@ static ssize_t tracing_resize_ring_buffer(unsigned long size)
                         atomic_inc(&max_tr.data[cpu]->disabled);
         }
 
-        if (size != global_trace.entries)
-                ret = __tracing_resize_ring_buffer(size);
+        if (cpu_id != RING_BUFFER_ALL_CPUS) {
+                /* make sure, this cpu is enabled in the mask */
+                if (!cpumask_test_cpu(cpu_id, tracing_buffer_mask)) {
+                        ret = -EINVAL;
+                        goto out;
+                }
+        }
 
+        ret = __tracing_resize_ring_buffer(size, cpu_id);
         if (ret < 0)
                 ret = -ENOMEM;
 
+out:
         for_each_tracing_cpu(cpu) {
                 if (global_trace.data[cpu])
                         atomic_dec(&global_trace.data[cpu]->disabled);
@@ -3157,7 +3193,8 @@ int tracing_update_buffers(void)
 
         mutex_lock(&trace_types_lock);
         if (!ring_buffer_expanded)
-                ret = __tracing_resize_ring_buffer(trace_buf_size);
+                ret = __tracing_resize_ring_buffer(trace_buf_size,
+                                                RING_BUFFER_ALL_CPUS);
         mutex_unlock(&trace_types_lock);
 
         return ret;
@@ -3181,7 +3218,8 @@ static int tracing_set_tracer(const char *buf)
         mutex_lock(&trace_types_lock);
 
         if (!ring_buffer_expanded) {
-                ret = __tracing_resize_ring_buffer(trace_buf_size);
+                ret = __tracing_resize_ring_buffer(trace_buf_size,
+                                                RING_BUFFER_ALL_CPUS);
                 if (ret < 0)
                         goto out;
                 ret = 0;
@@ -3207,8 +3245,8 @@ static int tracing_set_tracer(const char *buf)
                  * The max_tr ring buffer has some state (e.g. ring->clock) and
                  * we want preserve it.
                  */
-                ring_buffer_resize(max_tr.buffer, 1);
-                max_tr.entries = 1;
+                ring_buffer_resize(max_tr.buffer, 1, RING_BUFFER_ALL_CPUS);
+                set_buffer_entries(&max_tr, 1);
         }
         destroy_trace_option_files(topts);
 
@@ -3216,10 +3254,17 @@ static int tracing_set_tracer(const char *buf)
 
         topts = create_trace_option_files(current_trace);
         if (current_trace->use_max_tr) {
-                ret = ring_buffer_resize(max_tr.buffer, global_trace.entries);
-                if (ret < 0)
-                        goto out;
-                max_tr.entries = global_trace.entries;
+                int cpu;
+                /* we need to make per cpu buffer sizes equivalent */
+                for_each_tracing_cpu(cpu) {
+                        ret = ring_buffer_resize(max_tr.buffer,
+                                                global_trace.data[cpu]->entries,
+                                                cpu);
+                        if (ret < 0)
+                                goto out;
+                        max_tr.data[cpu]->entries =
+                                        global_trace.data[cpu]->entries;
+                }
         }
 
         if (t->init) {
@@ -3721,30 +3766,82 @@ out_err:
         goto out;
 }
 
+struct ftrace_entries_info {
+        struct trace_array      *tr;
+        int                     cpu;
+};
+
+static int tracing_entries_open(struct inode *inode, struct file *filp)
+{
+        struct ftrace_entries_info *info;
+
+        if (tracing_disabled)
+                return -ENODEV;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                return -ENOMEM;
+
+        info->tr = &global_trace;
+        info->cpu = (unsigned long)inode->i_private;
+
+        filp->private_data = info;
+
+        return 0;
+}
+
 static ssize_t
 tracing_entries_read(struct file *filp, char __user *ubuf,
                      size_t cnt, loff_t *ppos)
 {
-        struct trace_array *tr = filp->private_data;
-        char buf[96];
-        int r;
+        struct ftrace_entries_info *info = filp->private_data;
+        struct trace_array *tr = info->tr;
+        char buf[64];
+        int r = 0;
+        ssize_t ret;
 
         mutex_lock(&trace_types_lock);
-        if (!ring_buffer_expanded)
-                r = sprintf(buf, "%lu (expanded: %lu)\n",
-                            tr->entries >> 10,
-                            trace_buf_size >> 10);
-        else
-                r = sprintf(buf, "%lu\n", tr->entries >> 10);
+
+        if (info->cpu == RING_BUFFER_ALL_CPUS) {
+                int cpu, buf_size_same;
+                unsigned long size;
+
+                size = 0;
+                buf_size_same = 1;
+                /* check if all cpu sizes are same */
+                for_each_tracing_cpu(cpu) {
+                        /* fill in the size from first enabled cpu */
+                        if (size == 0)
+                                size = tr->data[cpu]->entries;
+                        if (size != tr->data[cpu]->entries) {
+                                buf_size_same = 0;
+                                break;
+                        }
+                }
+
+                if (buf_size_same) {
+                        if (!ring_buffer_expanded)
+                                r = sprintf(buf, "%lu (expanded: %lu)\n",
+                                            size >> 10,
+                                            trace_buf_size >> 10);
+                        else
+                                r = sprintf(buf, "%lu\n", size >> 10);
+                } else
+                        r = sprintf(buf, "X\n");
+        } else
+                r = sprintf(buf, "%lu\n", tr->data[info->cpu]->entries >> 10);
+
         mutex_unlock(&trace_types_lock);
 
-        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+        ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+        return ret;
 }
 
 static ssize_t
 tracing_entries_write(struct file *filp, const char __user *ubuf,
                       size_t cnt, loff_t *ppos)
 {
+        struct ftrace_entries_info *info = filp->private_data;
         unsigned long val;
         int ret;
 
@@ -3759,7 +3856,7 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
         /* value is in KB */
         val <<= 10;
 
-        ret = tracing_resize_ring_buffer(val);
+        ret = tracing_resize_ring_buffer(val, info->cpu);
         if (ret < 0)
                 return ret;
 
@@ -3768,6 +3865,16 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
         return cnt;
 }
 
+static int
+tracing_entries_release(struct inode *inode, struct file *filp)
+{
+        struct ftrace_entries_info *info = filp->private_data;
+
+        kfree(info);
+
+        return 0;
+}
+
 static ssize_t
 tracing_total_entries_read(struct file *filp, char __user *ubuf,
                                 size_t cnt, loff_t *ppos)
@@ -3779,7 +3886,7 @@ tracing_total_entries_read(struct file *filp, char __user *ubuf,
 
         mutex_lock(&trace_types_lock);
         for_each_tracing_cpu(cpu) {
-                size += tr->entries >> 10;
+                size += tr->data[cpu]->entries >> 10;
                 if (!ring_buffer_expanded)
                         expanded_size += trace_buf_size >> 10;
         }
@@ -3813,7 +3920,7 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp)
         if (trace_flags & TRACE_ITER_STOP_ON_FREE)
                 tracing_off();
         /* resize the ring buffer to 0 */
-        tracing_resize_ring_buffer(0);
+        tracing_resize_ring_buffer(0, RING_BUFFER_ALL_CPUS);
 
         return 0;
 }
@@ -4012,9 +4119,10 @@ static const struct file_operations tracing_pipe_fops = {
 };
 
 static const struct file_operations tracing_entries_fops = {
-        .open           = tracing_open_generic,
+        .open           = tracing_entries_open,
         .read           = tracing_entries_read,
         .write          = tracing_entries_write,
+        .release        = tracing_entries_release,
         .llseek         = generic_file_llseek,
 };
 
@@ -4466,6 +4574,9 @@ static void tracing_init_debugfs_percpu(long cpu)
 
         trace_create_file("stats", 0444, d_cpu,
                         (void *) cpu, &tracing_stats_fops);
+
+        trace_create_file("buffer_size_kb", 0444, d_cpu,
+                        (void *) cpu, &tracing_entries_fops);
 }
 
 #ifdef CONFIG_FTRACE_SELFTEST
@@ -4795,7 +4906,7 @@ static __init int tracer_init_debugfs(void)
                         (void *) TRACE_PIPE_ALL_CPU, &tracing_pipe_fops);
 
         trace_create_file("buffer_size_kb", 0644, d_tracer,
-                        &global_trace, &tracing_entries_fops);
+                        (void *) RING_BUFFER_ALL_CPUS, &tracing_entries_fops);
 
         trace_create_file("buffer_total_size_kb", 0444, d_tracer,
                         &global_trace, &tracing_total_entries_fops);
@@ -5056,7 +5167,6 @@ __init static int tracer_alloc_buffers(void)
                 WARN_ON(1);
                 goto out_free_cpumask;
         }
-        global_trace.entries = ring_buffer_size(global_trace.buffer);
         if (global_trace.buffer_disabled)
                 tracing_off();
 
@@ -5069,7 +5179,6 @@ __init static int tracer_alloc_buffers(void)
                 ring_buffer_free(global_trace.buffer);
                 goto out_free_cpumask;
         }
-        max_tr.entries = 1;
 #endif
 
         /* Allocate the first page for all buffers */
@@ -5078,6 +5187,11 @@ __init static int tracer_alloc_buffers(void)
                 max_tr.data[i] = &per_cpu(max_tr_data, i);
         }
 
+        set_buffer_entries(&global_trace, ring_buf_size);
+#ifdef CONFIG_TRACER_MAX_TRACE
+        set_buffer_entries(&max_tr, 1);
+#endif
+
         trace_init_cmdlines();
 
         register_tracer(&nop_trace);