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author | Jason Baron <jbaron@redhat.com> | 2011-03-16 17:29:47 -0400 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2011-04-04 12:48:08 -0400 |
commit | d430d3d7e646eb1eac2bb4aa244a644312e67c76 (patch) | |
tree | 0f52534f54d89e41042536ff2f1b2ce74c45c033 /include/linux/dynamic_debug.h | |
parent | ee5e51f51be755830f57445e268ba50e88ccbdbb (diff) | |
download | linux-stable-d430d3d7e646eb1eac2bb4aa244a644312e67c76.tar.gz linux-stable-d430d3d7e646eb1eac2bb4aa244a644312e67c76.tar.bz2 linux-stable-d430d3d7e646eb1eac2bb4aa244a644312e67c76.zip |
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/dynamic_debug.h')
-rw-r--r-- | include/linux/dynamic_debug.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h index 0c9653f11c18..e747ecd48e1c 100644 --- a/include/linux/dynamic_debug.h +++ b/include/linux/dynamic_debug.h @@ -1,8 +1,6 @@ #ifndef _DYNAMIC_DEBUG_H #define _DYNAMIC_DEBUG_H -#include <linux/jump_label.h> - /* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They * use independent hash functions, to reduce the chance of false positives. |