diff options
| author | Steven Rostedt <rostedt@goodmis.org> | 2013-11-14 22:57:29 -0500 |
|---|---|---|
| committer | Chris Mason <chris.mason@fusionio.com> | 2013-11-20 20:44:47 -0500 |
| commit | 4cd8587ce8fb79e49d1d6d1fc065f056188fb86a (patch) | |
| tree | 3139157ec70bf16dcc5a436eccd743d41397dc5e | |
| parent | 52a157592140ac76d9f15637543aecc2100f95cb (diff) | |
| download | linux-4cd8587ce8fb79e49d1d6d1fc065f056188fb86a.tar.bz2 | |
btrfs: Use trace condition for get_extent tracepoint
Doing an if statement to test some condition to know if we should
trigger a tracepoint is pointless when tracing is disabled. This just
adds overhead and wastes a branch prediction. This is why the
TRACE_EVENT_CONDITION() was created. It places the check inside the jump
label so that the branch does not happen unless tracing is enabled.
That is, instead of doing:
if (em)
trace_btrfs_get_extent(root, em);
Which is basically this:
if (em)
if (static_key(trace_btrfs_get_extent)) {
Using a TRACE_EVENT_CONDITION() we can just do:
trace_btrfs_get_extent(root, em);
And the condition trace event will do:
if (static_key(trace_btrfs_get_extent)) {
if (em) {
...
The static key is a non conditional jump (or nop) that is faster than
having to check if em is NULL or not.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
| -rw-r--r-- | fs/btrfs/inode.c | 3 | ||||
| -rw-r--r-- | include/trace/events/btrfs.h | 4 |
2 files changed, 4 insertions, 3 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index fd67b34e220d..f1a77449d032 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6187,8 +6187,7 @@ insert: write_unlock(&em_tree->lock); out: - if (em) - trace_btrfs_get_extent(root, em); + trace_btrfs_get_extent(root, em); if (path) btrfs_free_path(path); diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index f18b3b76e01e..4832d75dcbae 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -162,12 +162,14 @@ DEFINE_EVENT(btrfs__inode, btrfs_inode_evict, { EXTENT_FLAG_LOGGING, "LOGGING" }, \ { EXTENT_FLAG_FILLING, "FILLING" }) -TRACE_EVENT(btrfs_get_extent, +TRACE_EVENT_CONDITION(btrfs_get_extent, TP_PROTO(struct btrfs_root *root, struct extent_map *map), TP_ARGS(root, map), + TP_CONDITION(map), + TP_STRUCT__entry( __field( u64, root_objectid ) __field( u64, start ) |