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Commit 1879445d authored by Wang Nan's avatar Wang Nan Committed by Ingo Molnar
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perf/core: Set event's default ::overflow_handler() 

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: default avatarWang Nan <wangnan0@huawei.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 86e7972f

arch/arm/kernel/hw_breakpoint.c

+2 −2
Original line number Diff line number Diff line
@@ -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:

arch/arm64/kernel/hw_breakpoint.c

+2 −2
Original line number Diff line number Diff line
@@ -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:

include/linux/perf_event.h

+6 −0
Original line number Diff line number Diff line
@@ -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,

kernel/events/core.c

+8 −6
Original line number Diff line number Diff line
@@ -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);



	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;

	}



	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);