From 1879445dfa7bbd6fe21b09c5cc72f4934798afed Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Mon, 28 Mar 2016 06:41:30 +0000 Subject: [PATCH] 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: Wang Nan Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Alexander Shishkin Cc: Alexei Starovoitov Cc: Arnaldo Carvalho de Melo Cc: Brendan Gregg Cc: He Kuang Cc: Jiri Olsa Cc: Jiri Olsa Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: Zefan Li Link: http://lkml.kernel.org/r/1459147292-239310-3-git-send-email-wangnan0@huawei.com Signed-off-by: Ingo Molnar --- arch/arm/kernel/hw_breakpoint.c | 4 ++-- arch/arm64/kernel/hw_breakpoint.c | 4 ++-- include/linux/perf_event.h | 6 ++++++ kernel/events/core.c | 14 ++++++++------ 4 files changed, 18 insertions(+), 10 deletions(-) diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 6284779d64ee..b8df45883cf7 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -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: diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c index b45c95d34b83..4ef5373f9a76 100644 --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -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: diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 15588d4c581d..4065ca2d7149 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -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, diff --git a/kernel/events/core.c b/kernel/events/core.c index 51386e84293e..8c3b35f2a269 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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); -- 2.20.1