linux/include
Steven Rostedt 4cd8587ce8 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>
2013-11-20 20:44:47 -05:00
..
acpi ACPI / PM: Drop two functions that are not used any more 2013-10-17 15:44:48 +02:00
asm-generic mm: Fix generic hugetlb pte check return type. 2013-10-02 20:02:35 -04:00
clocksource ARM: SoC cleanups for 3.12 2013-09-06 13:21:16 -07:00
crypto crypto: scatterwalk - Add support for calculating number of SG elements 2013-08-21 21:27:58 +10:00
drm Revert "drm: mark context support as a legacy subsystem" 2013-09-20 08:32:59 +10:00
dt-bindings ARM: dts: Fix pinctrl mask for omap3 2013-10-08 10:37:29 -07:00
keys
kvm ARM: KVM: vgic: Bump VGIC_NR_IRQS to 256 2013-08-30 16:12:39 +03:00
linux ipc, msg: forbid negative values for "msg{max,mnb,mni}" 2013-11-03 10:53:11 -08:00
math-emu
media Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-09-05 14:54:29 -07:00
memory
misc
net mac802154: correct a typo in ieee802154_alloc_device() prototype 2013-10-21 18:56:23 -04:00
pcmcia
ras
rdma Merge branches 'cxgb4', 'flowsteer', 'ipoib', 'iser', 'mlx4', 'ocrdma' and 'qib' into for-next 2013-09-03 09:01:08 -07:00
rxrpc
scsi Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2013-09-12 16:11:45 -07:00
sound ASoC: rcar: fixup generation checker 2013-10-11 19:52:32 +01:00
target target/iscsi: Bump versions to v4.1.0 2013-09-10 20:23:37 -07:00
trace btrfs: Use trace condition for get_extent tracepoint 2013-11-20 20:44:47 -05:00
uapi Btrfs: add tests for find_lock_delalloc_range 2013-11-11 21:56:51 -05:00
video fbdev changes for 3.12: 2013-09-05 09:49:32 -07:00
xen Features: 2013-09-04 17:45:39 -07:00
Kbuild