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>
This commit is contained in:
committed by
Steven Rostedt
parent
ee5e51f51b
commit
d430d3d7e6
@ -505,7 +505,7 @@ struct perf_guest_info_callbacks {
|
||||
#include <linux/ftrace.h>
|
||||
#include <linux/cpu.h>
|
||||
#include <linux/irq_work.h>
|
||||
#include <linux/jump_label_ref.h>
|
||||
#include <linux/jump_label.h>
|
||||
#include <asm/atomic.h>
|
||||
#include <asm/local.h>
|
||||
|
||||
@ -1034,7 +1034,7 @@ static inline int is_software_event(struct perf_event *event)
|
||||
return event->pmu->task_ctx_nr == perf_sw_context;
|
||||
}
|
||||
|
||||
extern atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
|
||||
extern struct jump_label_key perf_swevent_enabled[PERF_COUNT_SW_MAX];
|
||||
|
||||
extern void __perf_sw_event(u32, u64, int, struct pt_regs *, u64);
|
||||
|
||||
@ -1063,22 +1063,21 @@ perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
|
||||
{
|
||||
struct pt_regs hot_regs;
|
||||
|
||||
JUMP_LABEL(&perf_swevent_enabled[event_id], have_event);
|
||||
return;
|
||||
|
||||
have_event:
|
||||
if (!regs) {
|
||||
perf_fetch_caller_regs(&hot_regs);
|
||||
regs = &hot_regs;
|
||||
if (static_branch(&perf_swevent_enabled[event_id])) {
|
||||
if (!regs) {
|
||||
perf_fetch_caller_regs(&hot_regs);
|
||||
regs = &hot_regs;
|
||||
}
|
||||
__perf_sw_event(event_id, nr, nmi, regs, addr);
|
||||
}
|
||||
__perf_sw_event(event_id, nr, nmi, regs, addr);
|
||||
}
|
||||
|
||||
extern atomic_t perf_sched_events;
|
||||
extern struct jump_label_key perf_sched_events;
|
||||
|
||||
static inline void perf_event_task_sched_in(struct task_struct *task)
|
||||
{
|
||||
COND_STMT(&perf_sched_events, __perf_event_task_sched_in(task));
|
||||
if (static_branch(&perf_sched_events))
|
||||
__perf_event_task_sched_in(task);
|
||||
}
|
||||
|
||||
static inline
|
||||
@ -1086,7 +1085,8 @@ void perf_event_task_sched_out(struct task_struct *task, struct task_struct *nex
|
||||
{
|
||||
perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0);
|
||||
|
||||
COND_STMT(&perf_sched_events, __perf_event_task_sched_out(task, next));
|
||||
if (static_branch(&perf_sched_events))
|
||||
__perf_event_task_sched_out(task, next);
|
||||
}
|
||||
|
||||
extern void perf_event_mmap(struct vm_area_struct *vma);
|
||||
|
Reference in New Issue
Block a user