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Questions tagged [ftrace]

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1
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1answer
27 views

How writing in debugfs controls ftrace?

Ftrace is controlled by manipulating the debug fs files. But how is it possible ? How kernel be aware of writing in this files and start its required actions?for exmple if 1 is written to tracing_on , ...
5
votes
1answer
351 views

Change format of syscall event trace output to ftrace

I enabled ftrace event tracing for sys_enter_openat syscall. The respective output format given at events/syscalls/sys_enter_openat/format is print fmt: "dfd: 0x%08lx, filename: 0x%08lx, flags: 0x%...
0
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1answer
31 views

Performance reduction activating trace-functionality in kernel

Is there any performance reduction to be expected from just activating trace (ftrace) functionality in the Linux kernel, but not using it at run time?
0
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1answer
34 views

functions folder in trace_stat folder of ftrace

I am learning ftrace, I read from the following link that I can enable function profiling using the 'function_profile_enabled' file. mount -t tracefs nodev /sys/kernel/tracing cd /sys/kernel/tracing ...
1
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0answers
254 views

how to use ftrace to function_trace a kernel modules interrupt?

I have a Banana Pi Arm device with 2 cores (1.2 GHz) running a Debian kernel which I enabled ftrace kernel debug options. I want to determine the amount of time spent in a kernel module function. The ...
1
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0answers
90 views

Tool for displaying timeline view of kernel/userspace execution trace

I've used the ftrace tool trace-cmd for recording scheduling tracepoints and syscall tracepoints. I can inspect them visually using the kernelshark GUI program. It dislays per-core timelines and per-...
1
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0answers
31 views

PMU and tracepoints

I am searching for information about the mechanism of creation of tracepoints. From this topic What are Kernel PMU event-s in perf_events list? and this blog brendangregg I've got that tracepoints are ...
1
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0answers
132 views

Function profiling on multi-core platform for specific PID using ftrace

I'm trying to use ftrace for function profiling based on function_profile_enabled as described here. I would like to capture function calls only for a certain PID using set_ftrace_pid as described in ...
2
votes
1answer
134 views

Ftrace time duration

I echoed 1 to tracing_on in /sys/kernel/debug/tracing directory and echoed 0 again after a second. However, the timestamp of the first entry is 216.852 and that of the last entry is 234.136 giving me ...
1
vote
1answer
629 views

ftrace not working? Probably a simple mistake

I am trying to monitor the function pci_bus_write_config_byte. I have a kernel module that I know for certain calls that function. echo "pci_bus_write_config_byte" > set_ftrace_filter Then I did ...
0
votes
1answer
599 views

How to get epoch time with trace-cmd (frontend for ftrace)?

<...>-32578 [001] **133767.868869**: kfree: call_site=ffffffff810e6f06 ptr=(nil) How to make trace-cmd report time in epoch time? The time by default is I think time since ...
6
votes
1answer
2k views

filter out certain processes and/or pids in ftrace?

I'm not sure if I'm thinking about this the right way (and please correct me if I'm wrong), but the following is my understanding of ftrace. In /sys/kernel/debug/tracing, there are the following ...