> ## Documentation Index > Fetch the complete documentation index at: https://dragonwingdocs.qualcomm.com/llms.txt > Use this file to discover all available pages before exploring further. # 跟踪内核函数 函数跟踪器（ftrace）提供跟踪实用程序，用于在运行时执行系统级性能分析和跟踪。 要使用 ftrace，请启用以下配置选项： * `CONFIG_FTRACE` * `CONFIG_HAVE_FUNCTION_TRACER` * `CONFIG_HAVE_FUNCTION_GRAPH_TRACER` * `CONFIG_HAVE_DYNAMIC_FTRACE` * `CONFIG_HAVE_FTRACE_MCOUNT_RECORD` 以下是 ftrace 可用于调试内核问题的一些操作： ## **将 ftrace 信息转储到 kmsg 缓冲区** 要随时从源代码中将 ftrace 信息转储到 kmsg 缓冲区，请调用 `ftrace_dump(DUMP_ALL)` 函数。 * 要增大 ftrace 环形缓冲区的大小，请运行以下命令： ```text theme={null} echo 200 > /sys/kernel/debug/tracing/buffer_size_kb ``` ## **启用工作队列跟踪** * 要启用工作队列跟踪，请运行以下命令： ```text theme={null} mount -t debugfs none /sys/kernel/debug ``` ```text theme={null} echo 1 > /sys/kernel/debug/tracing/events/workqueue/enable ``` ```text theme={null} echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event ``` ```text theme={null} cat /sys/kernel/debug/tracing/trace_pipe ``` ```text theme={null} cat /sys/kernel/debug/tracing/per_cpu/cpu1/trace ``` **示例输出：** ``` # tracer: nop # # entries-in-buffer/entries-written: 8682/8682 #P:1 # # \_-----=\> irqs-off # / \_----=\> need-resched # | / \_---=\> hardirq/softirq # || / \_--=\> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | \<...\>-4783 \[001\] d.s4 7524.354249: workqueue\_queue\_work: work struct=f2d91ee4 function=free\_css\_set\_work workqueue=f6427d80 req\_cpu=1 cpu=1 \-0 \[001\] d.h4 7524.424196: workqueue\_queue\_work: work struct=c10c32a8 function=def\_work\_fn workqueue=f55c7880 req\_cpu=1 cpu=4 e.process.gapps-4758 \[001\] dNs4 7524.454227: workqueue\_queue\_work: work struct=c4727fa4 function=free\_css\_set\_work workqueue=f6427d80 req\_cpu=1 cpu=1 Binder\_D-1693 \[001\] d.s3 7524.504198: workqueue\_queue\_work: work struct=cec6275c function=do\_dbs\_timer workqueue=f5424680 req\_cpu=1 cpu=1 \<...\>-4832 \[001\] d.h3 7524.574194: workqueue\_queue\_work: work struct=c10c32a8 function=def\_work\_fn workqueue=f55c7880 req\_cpu=1 cpu=4 ``` ## **启用中断请求（IRQ）跟踪** * 要启用中断跟踪，请运行以下命令： ```text theme={null} mount -t debugfs none /sys/kernel/debug ``` ```text theme={null} echo 1 > /sys/kernel/debug/tracing/events/irq/irq_handler_entry/enable ``` ```text theme={null} cat /sys/kernel/debug/tracing/trace ``` ```text theme={null} cat /sys/kernel/debug/tracing/trace_pipe ``` **示例输出：** ``` TASK-PID CPU# TIMESTAMP FUNCTION | | | | | adbd-302 \[000\] 295.075568: irq\_handler\_entry: irq=132 name=msm\_otg adbd-302 \[000\] 295.075599: irq\_handler\_entry: irq=132 name=msm\_hsusb adbd-302 \[000\] 295.075782: irq\_handler\_entry: irq=132 name=msm\_otg adbd-302 \[000\] 295.075782: irq\_handler\_entry: irq=132 name=msm\_hsusb \-0 \[000\] 295.076270: irq\_handler\_entry: irq=132 name=msm\_otg \-0 \[000\] 295.076270: irq\_handler\_entry: irq=132 name=msm\_hsusb \-0 \[000\] 295.077155: irq\_handler\_entry: irq=18 name=gp\_timer \-0 \[000\] 295.087166: irq\_handler\_entry: irq=18 name=gp\_timer \-0 \[000\] 295.097146: irq\_handler\_entry: irq=18 name=gp\_timer ``` ## **启用调度器跟踪** * 要跟踪任务之间的上下文切换，请运行以下命令以启用 `sched_switch` 跟踪器： ```text theme={null} mount -t debugfs none /sys/kernel/debug ``` ```text theme={null} echo 1 > /sys/kernel/debug/tracing/events/sched/sched_switch/enable ``` ```text theme={null} cat /sys/kernel/debug/tracing/trace ``` ```text theme={null} cat /sys/kernel/debug/tracing/trace_pipe ``` **示例输出：** ``` TASK-PID CPU# TIMESTAMP FUNCTION | | | | | WindowManagerPo-484 \[000\] 994.583135: sched\_switch: prev\_comm=WindowManagerPo SurfaceFlinger-334 \[000\] 994.583652: sched\_switch: prev\_comm=SurfaceFlinger WindowManagerPo-484 \[000\] 994.584320: sched\_switch: prev\_comm=WindowManagerPo GL updater-675 \[000\] 994.584370: sched\_switch: prev\_comm=GL updater WindowManagerPo-484 \[000\] 994.584424: sched\_switch: prev\_comm=WindowManagerPo ``` ## **查找 IRQ 延迟** * 要查找系统中的最大 IRQ 延迟和抢占延迟，请按如下方式为 `IRQOFF` 和 `PREEMPTIONOFF` 启用 ftrace 配置： > ```text theme={null} > CONFIG_IRQSOFF_TRACER =Y > CONFIG_PREEMPT_TRACER =Y > ``` > > 要使此配置生效，请重新编译内核。此配置可以有效检测毫秒级延迟。 * 要启用跟踪，请运行以下命令： > ```text theme={null} > echo 0 > /sys/kernel/debug/tracing/tracing_enabled > ``` > > ```text theme={null} > echo 0 > /sys/kernel/debug/tracing/tracing_max_latency > ``` > > ```text theme={null} > echo irqsoff > /sys/kernel/debug/tracing/current_tracer > ``` > > ```text theme={null} > echo 1 > /sys/kernel/debug/tracing/tracing_enabled > ``` > > ```text theme={null} > cat /sys/kernel/debug/tracing/trace > ``` * 要查找系统中观测到的最大延迟，请配置 `tracing_max_latency = 0`。要检测任何超过指定限制的延迟，请以微秒为单位设置阈值级别。例如， > ```text theme={null} > echo 2000 > /sys/kernel/debug/tracing/tracing_thresh > ``` 以下示例显示了 16 毫秒 IRQ 延迟的跟踪信息： ``` cat /sys/kernel/debug/tracing/trace # tracer: irqsoff # # WARNING: FUNCTION TRACING IS CORRUPTED # MAY BE MISSING FUNCTION EVENTS # irqsoff latency trace v1.1.5 on 3.4.0-perf-g7736d93-dirty # -------------------------------------------------------------------- # latency: 16757 us, #4/4, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:1) # ----------------- # | task: EventThread-534 (uid:1000 nice:-9 policy:0 rt\_prio:0) # ----------------- # =\> started at: _raw_spin\_lock\_irqsave # =\> ended at: _raw_spin\_unlock\_irqrestore # # # \_------=\> CPU# # / \_-----=\> irqs-off # | / \_----=\> need-resched # || / \_---=\> hardirq/softirq # ||| / \_--=\> preempt-depth # |||| / delay # cmd pid ||||| time | caller # / ||||| | / \<...\>-534 0d... 0us!: _raw_spin\_lock\_irqsave \<...\>-534 0d..1 16756us\+: _raw_spin\_unlock\_irqrestore \<...\>-534 0d..1 16758us\+: trace\_hardirqs\_on \<-\_raw\_spin\_unlock\_irqrestore \<...\>-534 0d..1 16780us : \ =\> trace\_hardirqs\_on =\> _raw_spin\_unlock\_irqrestore =\> clk\_enable =\> mdss\_dsi\_clk\_enable =\> mdss\_dsi\_clk\_ctrl =\> mdss\_dsi\_clk\_req =\> mdss\_dsi\_event\_handler =\> mdss\_mdp\_ctl\_intf\_event =\> mdss\_mdp\_cmd\_add\_vsync\_handler =\> mdss\_mdp\_overlay\_vsync\_ctrl =\> mdss\_mdp\_overlay\_ioctl\_handler =\> mdss\_fb\_ioctl =\> do\_fb\_ioctl =\> fb\_ioctl =\> do\_vfs\_ioctl =\> sys\_ioctl =\> ret\_fast\_syscall /sys/kernel/debug/tracing # ``` 有关更多信息，请参阅[内核文档](https://www.kernel.org/doc/Documentation)中提供的 `Documentation/trace/ftrace.txt` 文件。