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--- code:profiling [2017/12/22 14:25] – phil
+++ code:profiling [2020/03/29 12:13] (current) – external edit 127.0.0.1
@@ Line 5: / Line 5: @@
 ===== Dynamic Memory Allocation =====
-The biggest problems with dynamic memory management are:
+Typical problems with dynamic memory management are:
   - leaks and
   - corruption.
-While the later is rather tricky to analyse, for memleaks there is
+While the latter is rather tricky to analyse, for memleaks there is
 ''valgrind''. Invocation as follows:
 <code>
@@ Line 17: / Line 17: @@
 ===== Performance =====
-When programming, the code complexity (O-notation) is the main factor
+When programming, code complexity (O-notation) is the main factor identifying
-identifying CPU-intense algorithms. Reducing the code's complexity often
+CPU-intense algorithms. Reducing code complexity often doesn't suffice, though.
-doesn't suffice, though. E.g. IO-intense operations often lead to delays at
+E.g. IO-intense operations often lead to delays at run-time which isn't covered
-run-time which isn't covered by the O-notation, at all. This means that aside
+by O-notation, at all. This means that aside of complexity analysis, there
-of complexity analysis, there always should be run-time code execution time
+always should be run-time code execution time measurement.
-measurement. And this is where ''gprof'' comes into action:
+==== GProf ====
+''gprof'' is a profiler integrated into gcc. Enabled at compile-time, the
+program collects profiling data for later analysis using ''gprof'' tool:
 <code>
 $ gcc -pg -g test.c
 $ ./a.out
 $ gprof a.out gmon.out
+</code>
+==== Perf ====
+On recent kernels, ''perf'' is the best tool for the job. It may profile the
+whole system like with obsoleted OProfile but may be limited to a single
+program, also. Before executing the workload to profile (or while it is
+running), call:
+<code>
+# perf record
+</code>
+When done, finish recording using ''CTRL-c''. perf data will be written to //perf.data// in local directory. To analyse, call:
+<code>
+# perf report
 </code>
@@ Line 52: / Line 71: @@
 of //test.c//.
+If linking happens in a separate step, some additional flags have to be passed to linker:
+<code>
+CFLAGS  += -fprofile-arcs -ftest-coverage
+LDFLAGS += -lgcov --coverage
+</code>