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/asm-generic/vmlinux.lds.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/asm-generic/vmlinux.lds.h')
-rw-r--r-- | include/asm-generic/vmlinux.lds.h | 14 |
1 files changed, 4 insertions, 10 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 32c45e5fe0ab..79522166d7f1 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h | |||
@@ -170,6 +170,10 @@ | |||
170 | STRUCT_ALIGN(); \ | 170 | STRUCT_ALIGN(); \ |
171 | *(__tracepoints) \ | 171 | *(__tracepoints) \ |
172 | /* implement dynamic printk debug */ \ | 172 | /* implement dynamic printk debug */ \ |
173 | . = ALIGN(8); \ | ||
174 | VMLINUX_SYMBOL(__start___jump_table) = .; \ | ||
175 | *(__jump_table) \ | ||
176 | VMLINUX_SYMBOL(__stop___jump_table) = .; \ | ||
173 | . = ALIGN(8); \ | 177 | . = ALIGN(8); \ |
174 | VMLINUX_SYMBOL(__start___verbose) = .; \ | 178 | VMLINUX_SYMBOL(__start___verbose) = .; \ |
175 | *(__verbose) \ | 179 | *(__verbose) \ |
@@ -228,8 +232,6 @@ | |||
228 | \ | 232 | \ |
229 | BUG_TABLE \ | 233 | BUG_TABLE \ |
230 | \ | 234 | \ |
231 | JUMP_TABLE \ | ||
232 | \ | ||
233 | /* PCI quirks */ \ | 235 | /* PCI quirks */ \ |
234 | .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \ | 236 | .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \ |
235 | VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \ | 237 | VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \ |
@@ -589,14 +591,6 @@ | |||
589 | #define BUG_TABLE | 591 | #define BUG_TABLE |
590 | #endif | 592 | #endif |
591 | 593 | ||
592 | #define JUMP_TABLE \ | ||
593 | . = ALIGN(8); \ | ||
594 | __jump_table : AT(ADDR(__jump_table) - LOAD_OFFSET) { \ | ||
595 | VMLINUX_SYMBOL(__start___jump_table) = .; \ | ||
596 | *(__jump_table) \ | ||
597 | VMLINUX_SYMBOL(__stop___jump_table) = .; \ | ||
598 | } | ||
599 | |||
600 | #ifdef CONFIG_PM_TRACE | 594 | #ifdef CONFIG_PM_TRACE |
601 | #define TRACEDATA \ | 595 | #define TRACEDATA \ |
602 | . = ALIGN(4); \ | 596 | . = ALIGN(4); \ |