也就是说开启ftrace调用函数时,都会先调用_mcount,总是至少会执行两条指令,即使ftrace_trace_function没有被指向某个跟踪函数。 2.1.2 动态插桩 static ftrace一旦使能,对kernel中所有的函数(除开notrace、online、其他特殊函数)进行插桩,这带来的性能开销是惊人的,有可能导致人们弃用ftrace功能。 为了解决这个问题,内...
上述配置不一定全部打开,勾选自己需要的即可,通常我们选择CONFIG_FUNCTION_TRACER和CONFIG_HAVE_FUNCTION_GRAPH_TRACER即可,然后编译烧录到开发板。 通过make menuconfig的方式写入: Kernel hacking ---> Tracers ─> [*] Kernel Function Tracer [*] Kernel Function GraphTracer(NEW)// (下面还有几个追踪器的选项,...
每次线程切换时,kernel_stack也需要跟着切换。 // file: arch/x86/kernel/process_64.c/** switch_to(x,y) should switch tasks from x to y.** This could still be optimized:* - fold all the options into a flag word and test it with a single test.* - could test fs/gs bitsliced** Kp...
root@ubuntu:/sys/kernel/debug/tracing# cat trace# tracer: function_graph## CPU TASK/PID DURATION FUNCTION CALLS# | | | | | | | | |2) ls-46073 | | do_sys_open {2) ls-46073 | | getname {2) ls-46073 | | getname_flags {2) ls-46073 | | kmem_cache_alloc {2) ls-46073 |...
echo function_graph > current_tracer;//使用图形显示调用关系 echo ip_rcv > set_graph_function;//...
kernel.shmmax=268435456 (32位) kernel.shmmax=1073741824 (64位) kernel.msgmni=1024 fs.file-max...
如果是在x86的機器上,要Enable “Kernel Function Graph Trace”的功能,就要透過General setup --->Optimize for size ,選擇關閉 “Optimize for size “. 而在ARM平台上,目前沒有“Kernel Function Graph Trace”的選項,所以就不受此限制. 此外,在Linux Kernel 2.6.31 給ARM環境的組態中,目前並不支援Dynamic ...
tracer (which traces not only the function entry, but also the return of the function allowing you to create a call graph of the function flow), the stack tracer (where it is possible to see which function is taking up the most stack), kprobes (dynamic events) and even live kernel ...
$ sudo ipft -m 0xdeadbeef -t function_graph -o json <skip...> {"packet_id":"0xffff8dee8aea9700","timestamp":25340022557487,"processor_id":0,"function":"validate_xmit_xfrm","is_return":false} {"packet_id":"0xffff8dee8aea9700","timestamp":25340022558860,"processor_id":0,"functi...
Whyisthe kernel on-CPU so much? What code-paths? Which code-pathsarecausing CPU level 2 cache misses?Arethe CPUs stalled on memory I/O? Which code-pathsareallocating memory, and how much? Whatistriggering TCP retransmits?Isa certain kernel function being called, and how often?