Use prctl to enable/ disable perf for lower overhead

src/LinuxPerf.jl

@@ -321,6 +321,20 @@ function Base.show(io::IO, g::EventGroup)
     print(io, "\t", g.event_types[end], ")")
 end
 
+const SYS_prctl = Clong(157)
+const PR_TASK_PERF_EVENTS_DISABLE = Cint(31)
+const PR_TASK_PERF_EVENTS_ENABLE = Cint(32)
+
+# syscall is lower overhead than calling libc's prctl
+function enable_all!()
+    res = ccall(:syscall, Cint, (Clong, Clong...), SYS_prctl, PR_TASK_PERF_EVENTS_ENABLE)
+    Base.systemerror(:prctl, res < 0)
+end
+function disable_all!()
+    res = ccall(:syscall, Cint, (Clong, Clong...), SYS_prctl, PR_TASK_PERF_EVENTS_DISABLE)
+    Base.systemerror(:prctl, res < 0)
+end
+
 const PERF_EVENT_IOC_ENABLE =  UInt64(0x2400)
 const PERF_EVENT_IOC_DISABLE = UInt64(0x2401)
 const PERF_EVENT_IOC_RESET =   UInt64(0x2403)
@@ -1064,9 +1078,9 @@ macro pstats(args...)
             @debug dump_groups(groups)
             bench = make_bench_threaded(groups, threads = $(opts.threads))
             try
-                enable!(bench)
+                enable_all!()
                 val = $(esc(expr))
-                disable!(bench)
+                disable_all!()
                 # trick the compiler not to eliminate the code
                 stats = rand() < 0 ? val : Stats(bench)
                 return stats::Stats

test/runtests.jl

@@ -1,7 +1,7 @@
 using LinuxPerf
 using Test
 
-using LinuxPerf: make_bench, enable!, disable!, reset!, reasonable_defaults, counters, EventType, EventTypeExt, parse_groups
+using LinuxPerf: make_bench, enable!, disable!, reset!, reasonable_defaults, counters, EventType, EventTypeExt, parse_groups, enable_all!, disable_all!
 
 @testset "LinuxPerf" begin
 
@@ -21,7 +21,29 @@ using LinuxPerf: make_bench, enable!, disable!, reset!, reasonable_defaults, cou
         end
         g(zeros(10000))
 
-        counters(bench)
+        results = counters(bench)
+        close(bench)
+
+        true  # Succeeded without any exceptions...
+    end
+
+    @test begin
+        bench = make_bench(reasonable_defaults);
+        @noinline function g(a)
+            enable_all!()
+            c = 0
+            for x in a
+                if x > 0
+                    c += 1
+                end
+            end
+            disable_all!()
+            c
+        end
+        g(zeros(10000))
+
+        results = counters(bench)
+        close(bench)
 
         true  # Succeeded without any exceptions...
     end