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perf/core: Set event's default ::overflow_handler()

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Set a default event->overflow_handler in perf_event_alloc() so don't
need to check event->overflow_handler in __perf_event_overflow().
Following commits can give a different default overflow_handler.

Initial idea comes from Peter:

  http://lkml.kernel.org/r/20130708121557.GA17211@twins.programming.kicks-ass.net

Since the default value of event->overflow_handler is not NULL, existing
'if (!overflow_handler)' checks need to be changed.

is_default_overflow_handler() is introduced for this.

No extra performance overhead is introduced into the hot path because in the
original code we still need to read this handler from memory. A conditional
branch is avoided so actually we remove some instructions.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <pi3orama@163.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1459147292-239310-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Wang Nan 2016-03-28 06:41:30 +00:00 committed by Ingo Molnar
parent 86e7972f69
commit 1879445dfa
4 changed files with 18 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arm/kernel/hw_breakpoint.c
View File

@ -631,7 +631,7 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
info->address &= ~alignment_mask;
info->ctrl.len <<= offset;
if (!bp->overflow_handler) {
if (is_default_overflow_handler(bp)) {
/*
* Mismatch breakpoints are required for single-stepping
* breakpoints.
@ -754,7 +754,7 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
* mismatch breakpoint so we can single-step over the
* watchpoint trigger.
*/
if (!wp->overflow_handler)
if (is_default_overflow_handler(wp))
enable_single_step(wp, instruction_pointer(regs));
unlock:

4
arch/arm64/kernel/hw_breakpoint.c
View File

@ -616,7 +616,7 @@ static int breakpoint_handler(unsigned long unused, unsigned int esr,
perf_bp_event(bp, regs);
/* Do we need to handle the stepping? */
if (!bp->overflow_handler)
if (is_default_overflow_handler(bp))
step = 1;
unlock:
rcu_read_unlock();
@ -712,7 +712,7 @@ static int watchpoint_handler(unsigned long addr, unsigned int esr,
perf_bp_event(wp, regs);
/* Do we need to handle the stepping? */
if (!wp->overflow_handler)
if (is_default_overflow_handler(wp))
step = 1;
unlock:

6
include/linux/perf_event.h
View File

@ -838,6 +838,12 @@ extern void perf_event_output(struct perf_event *event,
struct perf_sample_data *data,
struct pt_regs *regs);
static inline bool
is_default_overflow_handler(struct perf_event *event)
{
return (event->overflow_handler == perf_event_output);
}
extern void
perf_event_header__init_id(struct perf_event_header *header,
struct perf_sample_data *data,

14
kernel/events/core.c
View File

@ -6628,10 +6628,7 @@ static int __perf_event_overflow(struct perf_event *event,
irq_work_queue(&event->pending);
}
if (event->overflow_handler)
event->overflow_handler(event, data, regs);
else
perf_event_output(event, data, regs);
event->overflow_handler(event, data, regs);
if (*perf_event_fasync(event) && event->pending_kill) {
event->pending_wakeup = 1;
@ -8152,8 +8149,13 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
context = parent_event->overflow_handler_context;
}
event->overflow_handler = overflow_handler;
event->overflow_handler_context = context;
if (overflow_handler) {
event->overflow_handler = overflow_handler;
event->overflow_handler_context = context;
} else {
event->overflow_handler = perf_event_output;
event->overflow_handler_context = NULL;
}
perf_event__state_init(event);