From 4cd8587ce8fb79e49d1d6d1fc065f056188fb86a Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 14 Nov 2013 22:57:29 -0500 Subject: [PATCH] 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 Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/inode.c | 3 +-- 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 ) -- 2.30.2