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d430d3d7e6
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>
103 lines
2.1 KiB
C
103 lines
2.1 KiB
C
#ifndef _LINUX_JUMP_LABEL_H
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#define _LINUX_JUMP_LABEL_H
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#include <linux/types.h>
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#include <linux/compiler.h>
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#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
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struct jump_label_key {
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atomic_t enabled;
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struct jump_entry *entries;
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#ifdef CONFIG_MODULES
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struct jump_label_mod *next;
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#endif
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};
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# include <asm/jump_label.h>
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# define HAVE_JUMP_LABEL
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#endif
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enum jump_label_type {
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JUMP_LABEL_DISABLE = 0,
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JUMP_LABEL_ENABLE,
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};
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struct module;
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#ifdef HAVE_JUMP_LABEL
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#ifdef CONFIG_MODULES
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#define JUMP_LABEL_INIT {{ 0 }, NULL, NULL}
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#else
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#define JUMP_LABEL_INIT {{ 0 }, NULL}
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#endif
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static __always_inline bool static_branch(struct jump_label_key *key)
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{
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return arch_static_branch(key);
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}
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extern struct jump_entry __start___jump_table[];
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extern struct jump_entry __stop___jump_table[];
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extern void jump_label_lock(void);
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extern void jump_label_unlock(void);
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extern void arch_jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type);
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extern void arch_jump_label_text_poke_early(jump_label_t addr);
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extern int jump_label_text_reserved(void *start, void *end);
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extern void jump_label_inc(struct jump_label_key *key);
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extern void jump_label_dec(struct jump_label_key *key);
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extern bool jump_label_enabled(struct jump_label_key *key);
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extern void jump_label_apply_nops(struct module *mod);
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#else
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#include <asm/atomic.h>
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#define JUMP_LABEL_INIT {ATOMIC_INIT(0)}
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struct jump_label_key {
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atomic_t enabled;
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};
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static __always_inline bool static_branch(struct jump_label_key *key)
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{
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if (unlikely(atomic_read(&key->enabled)))
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return true;
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return false;
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}
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static inline void jump_label_inc(struct jump_label_key *key)
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{
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atomic_inc(&key->enabled);
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}
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static inline void jump_label_dec(struct jump_label_key *key)
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{
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atomic_dec(&key->enabled);
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}
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static inline int jump_label_text_reserved(void *start, void *end)
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{
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return 0;
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}
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static inline void jump_label_lock(void) {}
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static inline void jump_label_unlock(void) {}
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static inline bool jump_label_enabled(struct jump_label_key *key)
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{
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return !!atomic_read(&key->enabled);
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}
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static inline int jump_label_apply_nops(struct module *mod)
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{
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return 0;
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}
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#endif
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#endif
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