diff options
author | Jason Baron <jbaron@redhat.com> | 2011-03-16 17:29:47 -0400 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2011-04-04 12:48:08 -0400 |
commit | d430d3d7e646eb1eac2bb4aa244a644312e67c76 (patch) | |
tree | 0f52534f54d89e41042536ff2f1b2ce74c45c033 /include/linux/jump_label.h | |
parent | ee5e51f51be755830f57445e268ba50e88ccbdbb (diff) |
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>
Diffstat (limited to 'include/linux/jump_label.h')
-rw-r--r-- | include/linux/jump_label.h | 89 |
1 files changed, 56 insertions, 33 deletions
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index 7880f18e4b8..83e745f3ead 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -1,20 +1,43 @@ #ifndef _LINUX_JUMP_LABEL_H #define _LINUX_JUMP_LABEL_H +#include <linux/types.h> +#include <linux/compiler.h> + #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) + +struct jump_label_key { + atomic_t enabled; + struct jump_entry *entries; +#ifdef CONFIG_MODULES + struct jump_label_mod *next; +#endif +}; + # include <asm/jump_label.h> # define HAVE_JUMP_LABEL #endif enum jump_label_type { + JUMP_LABEL_DISABLE = 0, JUMP_LABEL_ENABLE, - JUMP_LABEL_DISABLE }; struct module; #ifdef HAVE_JUMP_LABEL +#ifdef CONFIG_MODULES +#define JUMP_LABEL_INIT {{ 0 }, NULL, NULL} +#else +#define JUMP_LABEL_INIT {{ 0 }, NULL} +#endif + +static __always_inline bool static_branch(struct jump_label_key *key) +{ + return arch_static_branch(key); +} + extern struct jump_entry __start___jump_table[]; extern struct jump_entry __stop___jump_table[]; @@ -23,37 +46,37 @@ extern void jump_label_unlock(void); extern void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type); extern void arch_jump_label_text_poke_early(jump_label_t addr); -extern void jump_label_update(unsigned long key, enum jump_label_type type); -extern void jump_label_apply_nops(struct module *mod); extern int jump_label_text_reserved(void *start, void *end); +extern void jump_label_inc(struct jump_label_key *key); +extern void jump_label_dec(struct jump_label_key *key); +extern bool jump_label_enabled(struct jump_label_key *key); +extern void jump_label_apply_nops(struct module *mod); -#define jump_label_enable(key) \ - jump_label_update((unsigned long)key, JUMP_LABEL_ENABLE); +#else -#define jump_label_disable(key) \ - jump_label_update((unsigned long)key, JUMP_LABEL_DISABLE); +#include <asm/atomic.h> -#else +#define JUMP_LABEL_INIT {ATOMIC_INIT(0)} -#define JUMP_LABEL(key, label) \ -do { \ - if (unlikely(*key)) \ - goto label; \ -} while (0) +struct jump_label_key { + atomic_t enabled; +}; -#define jump_label_enable(cond_var) \ -do { \ - *(cond_var) = 1; \ -} while (0) +static __always_inline bool static_branch(struct jump_label_key *key) +{ + if (unlikely(atomic_read(&key->enabled))) + return true; + return false; +} -#define jump_label_disable(cond_var) \ -do { \ - *(cond_var) = 0; \ -} while (0) +static inline void jump_label_inc(struct jump_label_key *key) +{ + atomic_inc(&key->enabled); +} -static inline int jump_label_apply_nops(struct module *mod) +static inline void jump_label_dec(struct jump_label_key *key) { - return 0; + atomic_dec(&key->enabled); } static inline int jump_label_text_reserved(void *start, void *end) @@ -64,16 +87,16 @@ static inline int jump_label_text_reserved(void *start, void *end) static inline void jump_label_lock(void) {} static inline void jump_label_unlock(void) {} -#endif +static inline bool jump_label_enabled(struct jump_label_key *key) +{ + return !!atomic_read(&key->enabled); +} -#define COND_STMT(key, stmt) \ -do { \ - __label__ jl_enabled; \ - JUMP_LABEL(key, jl_enabled); \ - if (0) { \ -jl_enabled: \ - stmt; \ - } \ -} while (0) +static inline int jump_label_apply_nops(struct module *mod) +{ + return 0; +} + +#endif #endif |