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authorSteven Rostedt <srostedt@redhat.com>2010-10-08 13:51:48 -0400
committerSteven Rostedt <rostedt@goodmis.org>2010-10-19 13:22:36 -0400
commit747e94ae3d1b4c9bf5380e569f614eb9040b79e7 (patch)
tree29404444fa5106e6d3361fc6c85b4463777ec3a3 /kernel
parent51ea8a88aae425915b458bfe295f1f10a3d52781 (diff)
downloadop-kernel-dev-747e94ae3d1b4c9bf5380e569f614eb9040b79e7.zip
op-kernel-dev-747e94ae3d1b4c9bf5380e569f614eb9040b79e7.tar.gz
ring-buffer: Make write slow path out of line
Gcc inlines the slow path of the ring buffer write which can hurt performance. This patch simply forces the slow path function rb_move_tail() to always be a function. The ring_buffer_benchmark module with reader_disabled=1 shows that this patch changes the time to record an event from 135 ns to 132 ns. (3 ns or 2.22% improvement) Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ring_buffer.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index bca9637..0b88df8 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1823,7 +1823,10 @@ rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
local_sub(length, &tail_page->write);
}
-static struct ring_buffer_event *
+/*
+ * This is the slow path, force gcc not to inline it.
+ */
+static noinline struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long length, unsigned long tail,
struct buffer_page *tail_page, u64 *ts)
@@ -1943,7 +1946,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
tail = write - length;
/* See if we shot pass the end of this buffer page */
- if (write > BUF_PAGE_SIZE)
+ if (unlikely(write > BUF_PAGE_SIZE))
return rb_move_tail(cpu_buffer, length, tail,
tail_page, ts);
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