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When I use the perf record on my code, I find three choices for the --call-graph option: lbr (last branch record), dwarf and fp.
What is difference between these?
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perf record is used to sample events. Display a report that was previously created with perf record . Display a report file and an annotated version of the executed code. If debug symbols are installed, you will also see the source code displayed.
perf report is able to auto-detect whether a perf. data file contains branch stacks and it will automatically switch to the branch view mode, unless --no-branch-stack is used. --branch-history Add the addresses of sampled taken branches to the callstack. This allows to examine the path the program took to each sample.
The perf command is used as a primary interface to the Linux kernel performance monitoring capabilities and can record CPU performance counters and trace points.
The option --call-graph refers to the collection of call graphs / call chains, i.e. the function stack for a sample.
The default, fp, uses frame pointers. This is very efficient but can be unreliable, particularly for optimized code. By explicitly using -fno-omit-frame-pointer, you can ensure that this is available for your code. Nevertheless, the result for libraries may vary.
With dwarf, perf actually collects and stores a part of the stack memory itself and unwinds it with post-processing. This can be very resource consuming and may have limited stack depth. The default stack memory chunk is 8 kiB, but can be configured.
lbr stands for last branch records. This is a hardware mechanism support by Intel CPUs. This will probably offer the best performance at the cost of portability. lbr is also limited to userspace functions.
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