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>

3 files changed, 293 insertions, 147 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index cf8d11e91ef..2d5eb332082 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -449,6 +449,7 @@ struct ring_buffer_per_cpu {
         raw_spinlock_t                  reader_lock;    /* serialize readers */
         arch_spinlock_t                 lock;
         struct lock_class_key           lock_key;
+        unsigned int                    nr_pages;
         struct list_head                *pages;
         struct buffer_page              *head_page;     /* read from head */
         struct buffer_page              *tail_page;     /* write to tail */
@@ -466,10 +467,12 @@ struct ring_buffer_per_cpu {
         unsigned long                   read_bytes;
         u64                             write_stamp;
         u64                             read_stamp;
+        /* ring buffer pages to update, > 0 to add, < 0 to remove */
+        int                             nr_pages_to_update;
+        struct list_head                new_pages; /* new pages to add */
 };
 
 struct ring_buffer {
-        unsigned                        pages;
         unsigned                        flags;
         int                             cpus;
         atomic_t                        record_disabled;
@@ -963,14 +966,10 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
         return 0;
 }
 
-static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
-                             unsigned nr_pages)
+static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
 {
+        int i;
         struct buffer_page *bpage, *tmp;
-        LIST_HEAD(pages);
-        unsigned i;
-
-        WARN_ON(!nr_pages);
 
         for (i = 0; i < nr_pages; i++) {
                 struct page *page;
@@ -981,15 +980,13 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
                  */
                 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
                                     GFP_KERNEL | __GFP_NORETRY,
-                                    cpu_to_node(cpu_buffer->cpu));
+                                    cpu_to_node(cpu));
                 if (!bpage)
                         goto free_pages;
 
-                rb_check_bpage(cpu_buffer, bpage);
+                list_add(&bpage->list, pages);
 
-                list_add(&bpage->list, &pages);
-
-                page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
+                page = alloc_pages_node(cpu_to_node(cpu),
                                         GFP_KERNEL | __GFP_NORETRY, 0);
                 if (!page)
                         goto free_pages;
@@ -997,6 +994,27 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
                 rb_init_page(bpage->page);
         }
 
+        return 0;
+
+free_pages:
+        list_for_each_entry_safe(bpage, tmp, pages, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
+        }
+
+        return -ENOMEM;
+}
+
+static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
+                             unsigned nr_pages)
+{
+        LIST_HEAD(pages);
+
+        WARN_ON(!nr_pages);
+
+        if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
+                return -ENOMEM;
+
         /*
          * The ring buffer page list is a circular list that does not
          * start and end with a list head. All page list items point to
@@ -1005,20 +1023,15 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
         cpu_buffer->pages = pages.next;
         list_del(&pages);
 
+        cpu_buffer->nr_pages = nr_pages;
+
         rb_check_pages(cpu_buffer);
 
         return 0;
-
- free_pages:
-        list_for_each_entry_safe(bpage, tmp, &pages, list) {
-                list_del_init(&bpage->list);
-                free_buffer_page(bpage);
-        }
-        return -ENOMEM;
 }
 
 static struct ring_buffer_per_cpu *
-rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
+rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
         struct buffer_page *bpage;
@@ -1052,7 +1065,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
 
-        ret = rb_allocate_pages(cpu_buffer, buffer->pages);
+        ret = rb_allocate_pages(cpu_buffer, nr_pages);
         if (ret < 0)
                 goto fail_free_reader;
 
@@ -1113,7 +1126,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 {
         struct ring_buffer *buffer;
         int bsize;
-        int cpu;
+        int cpu, nr_pages;
 
         /* keep it in its own cache line */
         buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
@@ -1124,14 +1137,14 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
                 goto fail_free_buffer;
 
-        buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
+        nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
         buffer->flags = flags;
         buffer->clock = trace_clock_local;
         buffer->reader_lock_key = key;
 
         /* need at least two pages */
-        if (buffer->pages < 2)
-                buffer->pages = 2;
+        if (nr_pages < 2)
+                nr_pages = 2;
 
         /*
          * In case of non-hotplug cpu, if the ring-buffer is allocated
@@ -1154,7 +1167,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 
         for_each_buffer_cpu(buffer, cpu) {
                 buffer->buffers[cpu] =
-                        rb_allocate_cpu_buffer(buffer, cpu);
+                        rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
                 if (!buffer->buffers[cpu])
                         goto fail_free_buffers;
         }
@@ -1276,6 +1289,18 @@ out:
         raw_spin_unlock_irq(&cpu_buffer->reader_lock);
 }
 
+static void update_pages_handler(struct ring_buffer_per_cpu *cpu_buffer)
+{
+        if (cpu_buffer->nr_pages_to_update > 0)
+                rb_insert_pages(cpu_buffer, &cpu_buffer->new_pages,
+                                cpu_buffer->nr_pages_to_update);
+        else
+                rb_remove_pages(cpu_buffer, -cpu_buffer->nr_pages_to_update);
+        cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
+        /* reset this value */
+        cpu_buffer->nr_pages_to_update = 0;
+}
+
 /**
  * ring_buffer_resize - resize the ring buffer
  * @buffer: the buffer to resize.
@@ -1285,14 +1310,12 @@ out:
  *
  * Returns -1 on failure.
  */
-int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
+int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
+                        int cpu_id)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
-        unsigned nr_pages, rm_pages, new_pages;
-        struct buffer_page *bpage, *tmp;
-        unsigned long buffer_size;
-        LIST_HEAD(pages);
-        int i, cpu;
+        unsigned nr_pages;
+        int cpu;
 
         /*
          * Always succeed at resizing a non-existent buffer:
@@ -1302,15 +1325,11 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 
         size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
         size *= BUF_PAGE_SIZE;
-        buffer_size = buffer->pages * BUF_PAGE_SIZE;
 
         /* we need a minimum of two pages */
         if (size < BUF_PAGE_SIZE * 2)
                 size = BUF_PAGE_SIZE * 2;
 
-        if (size == buffer_size)
-                return size;
-
         atomic_inc(&buffer->record_disabled);
 
         /* Make sure all writers are done with this buffer. */
@@ -1321,68 +1340,56 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 
         nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
 
-        if (size < buffer_size) {
-
-                /* easy case, just free pages */
-                if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
-                        goto out_fail;
-
-                rm_pages = buffer->pages - nr_pages;
-
+        if (cpu_id == RING_BUFFER_ALL_CPUS) {
+                /* calculate the pages to update */
                 for_each_buffer_cpu(buffer, cpu) {
                         cpu_buffer = buffer->buffers[cpu];
-                        rb_remove_pages(cpu_buffer, rm_pages);
-                }
-                goto out;
-        }
 
-        /*
-         * This is a bit more difficult. We only want to add pages
-         * when we can allocate enough for all CPUs. We do this
-         * by allocating all the pages and storing them on a local
-         * link list. If we succeed in our allocation, then we
-         * add these pages to the cpu_buffers. Otherwise we just free
-         * them all and return -ENOMEM;
-         */
-        if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
-                goto out_fail;
+                        cpu_buffer->nr_pages_to_update = nr_pages -
+                                                        cpu_buffer->nr_pages;
 
-        new_pages = nr_pages - buffer->pages;
+                        /*
+                         * nothing more to do for removing pages or no update
+                         */
+                        if (cpu_buffer->nr_pages_to_update <= 0)
+                                continue;
 
-        for_each_buffer_cpu(buffer, cpu) {
-                for (i = 0; i < new_pages; i++) {
-                        struct page *page;
                         /*
-                         * __GFP_NORETRY flag makes sure that the allocation
-                         * fails gracefully without invoking oom-killer and
-                         * the system is not destabilized.
+                         * to add pages, make sure all new pages can be
+                         * allocated without receiving ENOMEM
                          */
-                        bpage = kzalloc_node(ALIGN(sizeof(*bpage),
-                                                  cache_line_size()),
-                                            GFP_KERNEL | __GFP_NORETRY,
-                                            cpu_to_node(cpu));
-                        if (!bpage)
-                                goto free_pages;
-                        list_add(&bpage->list, &pages);
-                        page = alloc_pages_node(cpu_to_node(cpu),
-                                                GFP_KERNEL | __GFP_NORETRY, 0);
-                        if (!page)
-                                goto free_pages;
-                        bpage->page = page_address(page);
-                        rb_init_page(bpage->page);
+                        INIT_LIST_HEAD(&cpu_buffer->new_pages);
+                        if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
+                                                &cpu_buffer->new_pages, cpu))
+                                /* not enough memory for new pages */
+                                goto no_mem;
                 }
-        }
 
-        for_each_buffer_cpu(buffer, cpu) {
-                cpu_buffer = buffer->buffers[cpu];
-                rb_insert_pages(cpu_buffer, &pages, new_pages);
-        }
+                /* wait for all the updates to complete */
+                for_each_buffer_cpu(buffer, cpu) {
+                        cpu_buffer = buffer->buffers[cpu];
+                        if (cpu_buffer->nr_pages_to_update) {
+                                update_pages_handler(cpu_buffer);
+                        }
+                }
+        } else {
+                cpu_buffer = buffer->buffers[cpu_id];
+                if (nr_pages == cpu_buffer->nr_pages)
+                        goto out;
 
-        if (RB_WARN_ON(buffer, !list_empty(&pages)))
-                goto out_fail;
+                cpu_buffer->nr_pages_to_update = nr_pages -
+                                                cpu_buffer->nr_pages;
+
+                INIT_LIST_HEAD(&cpu_buffer->new_pages);
+                if (cpu_buffer->nr_pages_to_update > 0 &&
+                        __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
+                                                &cpu_buffer->new_pages, cpu_id))
+                        goto no_mem;
+
+                update_pages_handler(cpu_buffer);
+        }
 
  out:
-        buffer->pages = nr_pages;
         put_online_cpus();
         mutex_unlock(&buffer->mutex);
 
@@ -1390,25 +1397,24 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 
         return size;
 
- free_pages:
-        list_for_each_entry_safe(bpage, tmp, &pages, list) {
-                list_del_init(&bpage->list);
-                free_buffer_page(bpage);
+ no_mem:
+        for_each_buffer_cpu(buffer, cpu) {
+                struct buffer_page *bpage, *tmp;
+                cpu_buffer = buffer->buffers[cpu];
+                /* reset this number regardless */
+                cpu_buffer->nr_pages_to_update = 0;
+                if (list_empty(&cpu_buffer->new_pages))
+                        continue;
+                list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
+                                        list) {
+                        list_del_init(&bpage->list);
+                        free_buffer_page(bpage);
+                }
         }
         put_online_cpus();
         mutex_unlock(&buffer->mutex);
         atomic_dec(&buffer->record_disabled);
         return -ENOMEM;
-
-        /*
-         * Something went totally wrong, and we are too paranoid
-         * to even clean up the mess.
-         */
- out_fail:
-        put_online_cpus();
-        mutex_unlock(&buffer->mutex);
-        atomic_dec(&buffer->record_disabled);
-        return -1;
 }
 EXPORT_SYMBOL_GPL(ring_buffer_resize);
 
@@ -1510,7 +1516,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
          * assign the commit to the tail.
          */
  again:
-        max_count = cpu_buffer->buffer->pages * 100;
+        max_count = cpu_buffer->nr_pages * 100;
 
         while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
                 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
@@ -3588,9 +3594,18 @@ EXPORT_SYMBOL_GPL(ring_buffer_read);
  * ring_buffer_size - return the size of the ring buffer (in bytes)
  * @buffer: The ring buffer.
  */
-unsigned long ring_buffer_size(struct ring_buffer *buffer)
+unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
 {
-        return BUF_PAGE_SIZE * buffer->pages;
+        /*
+         * Earlier, this method returned
+         *      BUF_PAGE_SIZE * buffer->nr_pages
+         * Since the nr_pages field is now removed, we have converted this to
+         * return the per cpu buffer value.
+         */
+        if (!cpumask_test_cpu(cpu, buffer->cpumask))
+                return 0;
+
+        return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
 }
 EXPORT_SYMBOL_GPL(ring_buffer_size);
 
@@ -3765,8 +3780,11 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
             !cpumask_test_cpu(cpu, buffer_b->cpumask))
                 goto out;
 
+        cpu_buffer_a = buffer_a->buffers[cpu];
+        cpu_buffer_b = buffer_b->buffers[cpu];
+
         /* At least make sure the two buffers are somewhat the same */
-        if (buffer_a->pages != buffer_b->pages)
+        if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
                 goto out;
 
         ret = -EAGAIN;
@@ -3780,9 +3798,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
         if (atomic_read(&buffer_b->record_disabled))
                 goto out;
 
-        cpu_buffer_a = buffer_a->buffers[cpu];
-        cpu_buffer_b = buffer_b->buffers[cpu];
-
         if (atomic_read(&cpu_buffer_a->record_disabled))
                 goto out;
 
@@ -4071,6 +4086,8 @@ static int rb_cpu_notify(struct notifier_block *self,
         struct ring_buffer *buffer =
                 container_of(self, struct ring_buffer, cpu_notify);
         long cpu = (long)hcpu;
+        int cpu_i, nr_pages_same;
+        unsigned int nr_pages;
 
         switch (action) {
         case CPU_UP_PREPARE:
@@ -4078,8 +4095,23 @@ static int rb_cpu_notify(struct notifier_block *self,
                 if (cpumask_test_cpu(cpu, buffer->cpumask))
                         return NOTIFY_OK;
 
+                nr_pages = 0;
+                nr_pages_same = 1;
+                /* check if all cpu sizes are same */
+                for_each_buffer_cpu(buffer, cpu_i) {
+                        /* fill in the size from first enabled cpu */
+                        if (nr_pages == 0)
+                                nr_pages = buffer->buffers[cpu_i]->nr_pages;
+                        if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
+                                nr_pages_same = 0;
+                                break;
+                        }
+                }
+                /* allocate minimum pages, user can later expand it */
+                if (!nr_pages_same)
+                        nr_pages = 2;
                 buffer->buffers[cpu] =
-                        rb_allocate_cpu_buffer(buffer, cpu);
+                        rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
                 if (!buffer->buffers[cpu]) {
                         WARN(1, "failed to allocate ring buffer on CPU %ld\n",
                              cpu);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bbcde546f9f..f11a285ee5b 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);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f9d85504f04..1c8b7c6f7b3 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -131,6 +131,7 @@ struct trace_array_cpu {
         atomic_t                disabled;
         void                    *buffer_page;   /* ring buffer spare */
 
+        unsigned long           entries;
         unsigned long           saved_latency;
         unsigned long           critical_start;
         unsigned long           critical_end;
@@ -152,7 +153,6 @@ struct trace_array_cpu {
  */
 struct trace_array {
         struct ring_buffer      *buffer;
-        unsigned long           entries;
         int                     cpu;
         int                     buffer_disabled;
         cycle_t                 time_start;