Add an example of the pstats macro to README (closes #21) (#25)

* make comments a bit shorter

* add example of pstats macro to README

* add example of specifying events

Author: bicycle1885

README.md

@@ -52,5 +52,42 @@ julia> data = zeros(10000); @measure g(data)
 └───────────────────────┴────────────┴─────────────┘
 ```
 
+The `@pstats' macro provides another (perhaps more concise) tool to measure
+performance events, which can be used in the same way as `@timed` of the
+standard library. The following example measures default events and reports its
+summary:
+```
+julia> using LinuxPerf, Random
+
+julia> mt = MersenneTwister(1234);
+
+julia> @pstats rand(mt, 1_000_000);  # compile
+
+julia> @pstats rand(mt, 1_000_000)  # default events
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+┌ cpu-cycles               2.88e+06   58.1%  #  1.2 cycles per ns
+│ stalled-cycles-frontend  9.50e+03   58.1%  #  0.3% of cycles
+└ stalled-cycles-backend   1.76e+06   58.1%  # 61.2% of cycles
+┌ instructions             1.11e+07   41.9%  #  3.9 insns per cycle
+│ branch-instructions      5.32e+05   41.9%  #  4.8% of insns
+└ branch-misses            2.07e+03   41.9%  #  0.4% of branch insns
+┌ task-clock               2.38e+06  100.0%  #  2.4 ms
+│ context-switches         0.00e+00  100.0%
+│ cpu-migrations           0.00e+00  100.0%
+└ page-faults              1.95e+03  100.0%
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+julia> insn = "(instructions,branch-instructions,branch-misses)"
+
+julia> @pstats insn rand(mt, 1_000_000)  # specific events
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+┌ instructions             1.05e+07  100.0%
+│ branch-instructions      5.03e+05  100.0%  #  4.8% of insns
+└ branch-misses            2.01e+03  100.0%  #  0.4% of branch insns
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+```
+
+See the documentation of `@pstats` for more details and available options.
+
 For more fine tuned performance profile examples, please check out the `test`
 directory.

src/LinuxPerf.jl

@@ -898,9 +898,9 @@ function printcounters(io::IO, groups::Vector{Vector{Counter}})
                     for (num, den, label) in [
                             ("stalled-cycles-frontend", "cpu-cycles", "cycles"),
                             ("stalled-cycles-backend", "cpu-cycles", "cycles"),
-                            ("branch-instructions", "instructions", "instructions"),
-                            ("branch-misses", "branch-instructions", "branch instructions"),
-                            ("cache-misses", "cache-references", "cache references"),
+                            ("branch-instructions", "instructions", "insns"),
+                            ("branch-misses", "branch-instructions", "branch insns"),
+                            ("cache-misses", "cache-references", "cache refs"),
                             ("L1-dcache-load-misses", "L1-dcache-loads", "dcache loads"),
                             ("L1-icache-load-misses", "L1-icache-loads", "icache loads"),
                             ("dTLB-load-misses", "dTLB-loads", "dTLB loads"),
@@ -1017,8 +1017,8 @@ julia> @pstats sort(xs)
 │ stalled-cycles-frontend  1.09e+07   49.7%  #  4.2% of cycles
 └ stalled-cycles-backend   7.07e+06   49.7%  #  2.7% of cycles
 ┌ instructions             1.96e+08   50.3%  #  0.8 insns per cycle
-│ branch-instructions      4.02e+07   50.3%  # 20.5% of instructions
-└ branch-misses            8.15e+06   50.3%  # 20.3% of branch instructions
+│ branch-instructions      4.02e+07   50.3%  # 20.5% of insns
+└ branch-misses            8.15e+06   50.3%  # 20.3% of branch insns
 ┌ task-clock               7.61e+07  100.0%  # 76.1 ms
 │ context-switches         7.00e+00  100.0%
 │ cpu-migrations           0.00e+00  100.0%
@@ -1029,8 +1029,8 @@ julia> @pstats "(cpu-cycles,instructions,branch-instructions,branch-misses),page
 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 ┌ cpu-cycles               2.64e+08  100.0%  #  3.5 cycles per ns
 │ instructions             1.86e+08  100.0%  #  0.7 insns per cycle
-│ branch-instructions      3.74e+07  100.0%  # 20.1% of instructions
-└ branch-misses            8.21e+06  100.0%  # 21.9% of branch instructions
+│ branch-instructions      3.74e+07  100.0%  # 20.1% of insns
+└ branch-misses            8.21e+06  100.0%  # 21.9% of branch insns
 ╶ page-faults              1.95e+03  100.0%
 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 ```