tracing: Add tracefs file buffer_percentage

Add a "buffer_percentage" file, that allows users to specify how much of the
buffer (percentage of pages) need to be filled before waking up a task
blocked on a per cpu trace_pipe_raw file.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 23 insertions, 16 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9edb628603ab..5434c16f2192 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -489,6 +489,7 @@ struct ring_buffer_per_cpu {
         local_t                         commits;
         local_t                         pages_touched;
         local_t                         pages_read;
+        long                            last_pages_touch;
         size_t                          shortest_full;
         unsigned long                   read;
         unsigned long                   read_bytes;
@@ -2632,7 +2633,9 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
 static __always_inline void
 rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
 {
-        bool pagebusy;
+        size_t nr_pages;
+        size_t dirty;
+        size_t full;
 
         if (buffer->irq_work.waiters_pending) {
                 buffer->irq_work.waiters_pending = false;
@@ -2646,24 +2649,27 @@ rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
                 irq_work_queue(&cpu_buffer->irq_work.work);
         }
 
-        pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+        if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
+                return;
 
-        if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
-                size_t nr_pages;
-                size_t dirty;
-                size_t full;
+        if (cpu_buffer->reader_page == cpu_buffer->commit_page)
+                return;
 
-                full = cpu_buffer->shortest_full;
-                nr_pages = cpu_buffer->nr_pages;
-                dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
-                if (full && nr_pages && (dirty * 100) <= full * nr_pages)
-                        return;
+        if (!cpu_buffer->irq_work.full_waiters_pending)
+                return;
 
-                cpu_buffer->irq_work.wakeup_full = true;
-                cpu_buffer->irq_work.full_waiters_pending = false;
-                /* irq_work_queue() supplies it's own memory barriers */
-                irq_work_queue(&cpu_buffer->irq_work.work);
-        }
+        cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
+
+        full = cpu_buffer->shortest_full;
+        nr_pages = cpu_buffer->nr_pages;
+        dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
+        if (full && nr_pages && (dirty * 100) <= full * nr_pages)
+                return;
+
+        cpu_buffer->irq_work.wakeup_full = true;
+        cpu_buffer->irq_work.full_waiters_pending = false;
+        /* irq_work_queue() supplies it's own memory barriers */
+        irq_work_queue(&cpu_buffer->irq_work.work);
 }
 
 /*
@@ -4394,6 +4400,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         local_set(&cpu_buffer->commits, 0);
         local_set(&cpu_buffer->pages_touched, 0);
         local_set(&cpu_buffer->pages_read, 0);
+        cpu_buffer->last_pages_touch = 0;
         cpu_buffer->shortest_full = 0;
         cpu_buffer->read = 0;
         cpu_buffer->read_bytes = 0;