mirror of
https://github.com/torvalds/linux.git
synced 2024-11-07 20:51:47 +00:00
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>
36 lines
602 B
C
36 lines
602 B
C
#ifndef _ASM_SPARC_JUMP_LABEL_H
|
|
#define _ASM_SPARC_JUMP_LABEL_H
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
#include <linux/types.h>
|
|
|
|
#define JUMP_LABEL_NOP_SIZE 4
|
|
|
|
static __always_inline bool arch_static_branch(struct jump_label_key *key)
|
|
{
|
|
asm goto("1:\n\t"
|
|
"nop\n\t"
|
|
"nop\n\t"
|
|
".pushsection __jump_table, \"aw\"\n\t"
|
|
".align 4\n\t"
|
|
".word 1b, %l[l_yes], %c0\n\t"
|
|
".popsection \n\t"
|
|
: : "i" (key) : : l_yes);
|
|
return false;
|
|
l_yes:
|
|
return true;
|
|
}
|
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
typedef u32 jump_label_t;
|
|
|
|
struct jump_entry {
|
|
jump_label_t code;
|
|
jump_label_t target;
|
|
jump_label_t key;
|
|
};
|
|
|
|
#endif
|