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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>
85 lines
2.6 KiB
C
85 lines
2.6 KiB
C
#ifndef _DYNAMIC_DEBUG_H
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#define _DYNAMIC_DEBUG_H
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/* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which
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* bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
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* use independent hash functions, to reduce the chance of false positives.
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*/
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extern long long dynamic_debug_enabled;
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extern long long dynamic_debug_enabled2;
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/*
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* An instance of this structure is created in a special
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* ELF section at every dynamic debug callsite. At runtime,
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* the special section is treated as an array of these.
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*/
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struct _ddebug {
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/*
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* These fields are used to drive the user interface
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* for selecting and displaying debug callsites.
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*/
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const char *modname;
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const char *function;
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const char *filename;
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const char *format;
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unsigned int lineno:24;
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/*
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* The flags field controls the behaviour at the callsite.
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* The bits here are changed dynamically when the user
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* writes commands to <debugfs>/dynamic_debug/control
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*/
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#define _DPRINTK_FLAGS_PRINT (1<<0) /* printk() a message using the format */
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#define _DPRINTK_FLAGS_INCL_MODNAME (1<<1)
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#define _DPRINTK_FLAGS_INCL_FUNCNAME (1<<2)
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#define _DPRINTK_FLAGS_INCL_LINENO (1<<3)
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#define _DPRINTK_FLAGS_INCL_TID (1<<4)
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#define _DPRINTK_FLAGS_DEFAULT 0
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unsigned int flags:8;
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char enabled;
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} __attribute__((aligned(8)));
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int ddebug_add_module(struct _ddebug *tab, unsigned int n,
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const char *modname);
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#if defined(CONFIG_DYNAMIC_DEBUG)
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extern int ddebug_remove_module(const char *mod_name);
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extern int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
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__attribute__ ((format (printf, 2, 3)));
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#define dynamic_pr_debug(fmt, ...) do { \
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static struct _ddebug descriptor \
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__used \
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__attribute__((section("__verbose"), aligned(8))) = \
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{ KBUILD_MODNAME, __func__, __FILE__, fmt, __LINE__, \
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_DPRINTK_FLAGS_DEFAULT }; \
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if (unlikely(descriptor.enabled)) \
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__dynamic_pr_debug(&descriptor, pr_fmt(fmt), ##__VA_ARGS__); \
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} while (0)
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#define dynamic_dev_dbg(dev, fmt, ...) do { \
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static struct _ddebug descriptor \
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__used \
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__attribute__((section("__verbose"), aligned(8))) = \
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{ KBUILD_MODNAME, __func__, __FILE__, fmt, __LINE__, \
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_DPRINTK_FLAGS_DEFAULT }; \
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if (unlikely(descriptor.enabled)) \
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dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); \
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} while (0)
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#else
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static inline int ddebug_remove_module(const char *mod)
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{
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return 0;
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}
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#define dynamic_pr_debug(fmt, ...) \
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do { if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); } while (0)
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#define dynamic_dev_dbg(dev, fmt, ...) \
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do { if (0) dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); } while (0)
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#endif
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#endif
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