---Ftrace---

2023-10-13 10:24:34

Ftrace功能
function_profile_enabled	跟踪函数的profile
kprobe_events	创建event并跟踪，见kprobe

Kprobe
实现文件 trace_kprobe.c	主要参考函数为 __trace_kprobe_create arm64的实现时通过将原指令替换为BRK指令实现。
echo 'p task_tick_fair' > kprobe_events	添加 task_tick_fair event，会生成 events/kprobes/p_task_tick_fair_0
echo '- task_tick_fair' > kprobe_events	删除上面添加的event
echo 'p task_tick_fair $arg1 $arg2 $arg3' > kprobe_events	task_tick_fair的定义为 task_tick_fair(struct rq rq, struct task_struct curr, int queued) 这里arg1对于与rq，arg2对应于curr，arg3对应与queued
echo 'p task_tick_fair rq=$arg1 cur=$arg2 queued=$arg3' > kprobe_events	同上，只是在显示时将arg1显示为rq，方便调试
echo 'r __pick_next_task_fair $retval' > kprobe_events	添加 return probe，添加成功，但获取不到想要的结果

perf
perf probe -x /home/xxx/test/a.out /home/xxx/test/main.c:4 argc argv k	在main.c的第4行probe，打印出argc argv和k这三个参数
perf probe /home/xxx/test/a.out main argc argv	在函数main的入口处probe，打印出argc和argv
perf probe /home/xxx/test/a.out main:4	在main的第4行插入probe
perf probe scheduler*	在所有scheduler开头的函数入口处probe
root@kickseed:~/test# perf probe -V do_sys_open Available variables at do_sys_open @<do_sys_open+0> char* filename int dfd int flags struct open_flags op umode_t mode	查看do_sys_open有哪些变量可以在probe中使用
root@kickseed:~/test# perf probe -V do_sys_open --range Available variables at do_sys_open @<do_sys_open+0> [INV] int fd @<do_sys_open+[302-307,307-346,427-657,669-690]> [INV] struct filename* tmp @<do_sys_open+[284-293,293-348,427-657,669-690]> [VAL] char* filename @<do_sys_open+[0-283,320-333,354-427,657-669]> [VAL] int dfd @<do_sys_open+[0-320,320-352,352-354,354-451,657-669,685-690]> [VAL] int flags @<do_sys_open+[0-63,63-344,354-690]> [VAL] struct open_flags op @<do_sys_open+[0-690]> [VAL] umode_t mode @<do_sys_open+[0-350,354-620,652-690]>	查看变量的有效范围
root@kickseed:~/test# perf probe do_sys_open filename:string flags 'op.mode'	a.out-14389 [000] .... 2459018.446122: do_sys_open: (do_sys_open+0x0/0x2c0) filename_string="/lib/x86_64-linux-gnu/libdl.so.2" flags=557056 mode=0xff20
perf probe __pick_next_task_fair%return $retval	添加ret probe,但没有返回值，待查
perf probe -k /userdata/vmlinux -m /mps/ko/cexxxxv100_isp.ko cnispCreatePipe pipe=viPipe attr='pstPipeAttr->u32Maxw'	perf向ko中添加kprobe event
perf buildid-cache -a /mps/ko/ceisp.ko	将ko加载到buildid中，路径是 /root/.debug/.build-id
perf top --symbols kfree	// 仅显示指定的符号
echo "wakeup_latency u64 lat; pid_t pid; int prio" >> /sys/kernel/debug/tracing/synthetic_events echo 'hist:keys=$saved_pid:saved_pid=pid:ts0=common_timestamp.usecs if comm=="time"' >> /sys/kernel/debug/tracing/events/sched/sched_waking/trigger echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).wakeup_latency($wakeup_lat, $saved_pid, next_prio) if next_comm=="time"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger echo 'hist:keys=pid,prio,lat:sort=pid,lat' >> /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger	添加一个synthetic event，统计latency。
mount -t debugfs nodev /proc/sys/debug echo schedule > /proc/sys/debug/tracingset_graph_function echo function_graph > /proc/sys/debug/tracingcurrent_tracer echo 3 > /proc/sys/debug/tracingmax_graph_depth echo 1 > /proc/sys/debug/tracingtracing_on echo 'r:sched_ret schedule' >> /proc/sys/debug/tracing/kprobe_events echo 'p:sched_ent schedule' >> /proc/sys/debug/tracing/kprobe_events echo 'hist:keys=common_pid:ts0=common_timestamp.usecs' >> /proc/sys/debug/tracing/events/kprobes/sched_ent/trigger echo 'hist:keys=common_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmax($wakeup_lat).snapshot()' >> /proc/sys/debug/tracing/events/kprobes/sched_ret/trigger	统计schedule函数的执行时间，并在最大时做snapshot。