Merge tag 'trace-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - Rework of the kprobe/uprobe and synthetic events to consolidate all
   the dynamic event code. This will make changes in the future easier.

 - Partial rewrite of the function graph tracing infrastructure. This
   will allow for multiple users of hooking onto functions to get the
   callback (return) of the function. This is the ground work for having
   kprobes and function graph tracer using one code base.

 - Clean up of the histogram code that will facilitate adding more
   features to the histograms in the future.

 - Addition of str_has_prefix() and a few use cases. There currently is
   a similar function strstart() that is used in a few places, but only
   returns a bool and not a length. These instances will be removed in
   the future to use str_has_prefix() instead.

 - A few other various clean ups as well.

* tag 'trace-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (57 commits)
  tracing: Use the return of str_has_prefix() to remove open coded numbers
  tracing: Have the historgram use the result of str_has_prefix() for len of prefix
  tracing: Use str_has_prefix() instead of using fixed sizes
  tracing: Use str_has_prefix() helper for histogram code
  string.h: Add str_has_prefix() helper function
  tracing: Make function ‘ftrace_exports’ static
  tracing: Simplify printf'ing in seq_print_sym
  tracing: Avoid -Wformat-nonliteral warning
  tracing: Merge seq_print_sym_short() and seq_print_sym_offset()
  tracing: Add hist trigger comments for variable-related fields
  tracing: Remove hist trigger synth_var_refs
  tracing: Use hist trigger's var_ref array to destroy var_refs
  tracing: Remove open-coding of hist trigger var_ref management
  tracing: Use var_refs[] for hist trigger reference checking
  tracing: Change strlen to sizeof for hist trigger static strings
  tracing: Remove unnecessary hist trigger struct field
  tracing: Fix ftrace_graph_get_ret_stack() to use task and not current
  seq_buf: Use size_t for len in seq_buf_puts()
  seq_buf: Make seq_buf_puts() null-terminate the buffer
  arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack
  ...

1 files changed, 81 insertions, 13 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 4f3247a53259..06e864a334bb 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -487,6 +487,10 @@ struct ring_buffer_per_cpu {
         local_t                         dropped_events;
         local_t                         committing;
         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;
         u64                             write_stamp;
@@ -529,6 +533,41 @@ struct ring_buffer_iter {
         u64                             read_stamp;
 };
 
+/**
+ * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
+ * @buffer: The ring_buffer to get the number of pages from
+ * @cpu: The cpu of the ring_buffer to get the number of pages from
+ *
+ * Returns the number of pages used by a per_cpu buffer of the ring buffer.
+ */
+size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu)
+{
+        return buffer->buffers[cpu]->nr_pages;
+}
+
+/**
+ * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
+ * @buffer: The ring_buffer to get the number of pages from
+ * @cpu: The cpu of the ring_buffer to get the number of pages from
+ *
+ * Returns the number of pages that have content in the ring buffer.
+ */
+size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu)
+{
+        size_t read;
+        size_t cnt;
+
+        read = local_read(&buffer->buffers[cpu]->pages_read);
+        cnt = local_read(&buffer->buffers[cpu]->pages_touched);
+        /* The reader can read an empty page, but not more than that */
+        if (cnt < read) {
+                WARN_ON_ONCE(read > cnt + 1);
+                return 0;
+        }
+
+        return cnt - read;
+}
+
 /*
  * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
  *
@@ -556,7 +595,7 @@ static void rb_wake_up_waiters(struct irq_work *work)
  * as data is added to any of the @buffer's cpu buffers. Otherwise
  * it will wait for data to be added to a specific cpu buffer.
  */
-int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full)
 {
         struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
         DEFINE_WAIT(wait);
@@ -571,7 +610,7 @@ int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
         if (cpu == RING_BUFFER_ALL_CPUS) {
                 work = &buffer->irq_work;
                 /* Full only makes sense on per cpu reads */
-                full = false;
+                full = 0;
         } else {
                 if (!cpumask_test_cpu(cpu, buffer->cpumask))
                         return -ENODEV;
@@ -623,15 +662,22 @@ int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
                     !ring_buffer_empty_cpu(buffer, cpu)) {
                         unsigned long flags;
                         bool pagebusy;
+                        size_t nr_pages;
+                        size_t dirty;
 
                         if (!full)
                                 break;
 
                         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
                         pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+                        nr_pages = cpu_buffer->nr_pages;
+                        dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
+                        if (!cpu_buffer->shortest_full ||
+                            cpu_buffer->shortest_full < full)
+                                cpu_buffer->shortest_full = full;
                         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
-
-                        if (!pagebusy)
+                        if (!pagebusy &&
+                            (!nr_pages || (dirty * 100) > full * nr_pages))
                                 break;
                 }
 
@@ -1054,6 +1100,7 @@ static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
         old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
         old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
 
+        local_inc(&cpu_buffer->pages_touched);
         /*
          * Just make sure we have seen our old_write and synchronize
          * with any interrupts that come in.
@@ -2586,7 +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;
@@ -2600,14 +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) {
-                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);
-        }
+        if (cpu_buffer->reader_page == cpu_buffer->commit_page)
+                return;
+
+        if (!cpu_buffer->irq_work.full_waiters_pending)
+                return;
+
+        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);
 }
 
 /*
@@ -3732,13 +3794,15 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
                 goto spin;
 
         /*
-         * Yeah! We succeeded in replacing the page.
+         * Yay! We succeeded in replacing the page.
          *
          * Now make the new head point back to the reader page.
          */
         rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
         rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
 
+        local_inc(&cpu_buffer->pages_read);
+
         /* Finally update the reader page to the new head */
         cpu_buffer->reader_page = reader;
         cpu_buffer->reader_page->read = 0;
@@ -4334,6 +4398,10 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         local_set(&cpu_buffer->entries, 0);
         local_set(&cpu_buffer->committing, 0);
         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;