linux/arch/x86
Jason Baron d430d3d7e6 jump label: Introduce static_branch() interface
Introduce:

static __always_inline bool static_branch(struct jump_label_key *key);

instead of the old JUMP_LABEL(key, label) macro.

In this way, jump labels become really easy to use:

Define:

        struct jump_label_key jump_key;

Can be used as:

        if (static_branch(&jump_key))
                do unlikely code

enable/disale via:

        jump_label_inc(&jump_key);
        jump_label_dec(&jump_key);

that's it!

For the jump labels disabled case, the static_branch() becomes an
atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(),
atomic_dec() operations. We show testing results for this change below.

Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct.

Since we now require a 'struct jump_label_key *key', we can store a pointer into
the jump table addresses. In this way, we can enable/disable jump labels, in
basically constant time. This change allows us to completely remove the previous
hashtable scheme. Thanks to Peter Zijlstra for this re-write.

Testing:

I ran a series of 'tbench 20' runs 5 times (with reboots) for 3
configurations, where tracepoints were disabled.

jump label configured in
avg: 815.6

jump label *not* configured in (using atomic reads)
avg: 800.1

jump label *not* configured in (regular reads)
avg: 803.4

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110316212947.GA8792@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Suggested-by: H. Peter Anvin <hpa@linux.intel.com>
Tested-by: David Daney <ddaney@caviumnetworks.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-04-04 12:48:08 -04:00
..
boot x86, build: Make sure mkpiggy fails on read error 2011-03-01 16:32:03 -08:00
configs defconfig reduction 2010-08-14 22:26:53 +02:00
crypto crypto: aesni-intel - fixed problem with packets that are not multiple of 64bytes 2011-03-27 10:29:39 +08:00
ia32 x86: mark associated mm when running a task in 32 bit compatibility mode 2011-03-23 16:36:53 -04:00
include/asm jump label: Introduce static_branch() interface 2011-04-04 12:48:08 -04:00
kernel jump label: Introduce static_branch() interface 2011-04-04 12:48:08 -04:00
kvm Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-18 10:45:21 -07:00
lguest x86: Fix common misspellings 2011-03-18 10:39:30 +01:00
lib percpu: Omit segment prefix in the UP case for cmpxchg_double 2011-03-27 19:25:36 -07:00
math-emu x86, fpu: Unbreak FPU emulation 2010-05-10 13:37:16 -07:00
mm Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2011-03-23 20:51:42 -07:00
oprofile Merge branch 'core' of git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile into perf/urgent 2011-03-29 09:32:28 +02:00
pci Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6 2011-03-18 10:56:44 -07:00
platform mfd: OLPC: Clean up names to match what OLPC actually uses 2011-03-27 00:09:31 +01:00
power x86, tsc, sched: Recompute cyc2ns_offset's during resume from sleep states 2010-08-20 14:59:02 +02:00
tools x86: Remove trailing spaces in messages 2010-02-07 17:47:51 +01:00
vdso mm: arch: rename in_gate_area_no_task to in_gate_area_no_mm 2011-03-23 16:36:55 -04:00
video
xen Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-22 10:41:36 -07:00
.gitignore add random binaries to .gitignore 2010-04-08 11:34:34 +02:00
Kbuild x86: Add platform directory 2010-10-27 14:30:01 +02:00
Kconfig Merge branch 'syscore' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6 2011-03-25 21:07:59 -07:00
Kconfig.cpu x86: Fix common misspellings 2011-03-18 10:39:30 +01:00
Kconfig.debug kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
Makefile Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 13:06:00 -07:00
Makefile_32.cpu jump label: Add work around to i386 gcc asm goto bug 2010-10-29 14:45:29 -04:00