factor out check.go; update some traces

coffee/README.md

@@ -5,6 +5,8 @@ go-torch -b ./sync-$mode.pprof -f ./torch-$mode.svg
 end
 
 # https://github.com/aclements/perflock
+# Prevents multiple benchmarks from running at once,
+# and keeps CPU from running too hot and so triggering CPU throttling.
 
 # Disable hyperthreading on 12-core Linux machine
 sudo su root

coffee/main.go

@@ -16,7 +16,6 @@ import (
 	"os"
 	"runtime"
 	"runtime/trace"
-	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -576,31 +575,3 @@ func modeParam(mode, prefix string, n *int) bool {
 	}
 	return true
 }
-
-func checkVariance() {
-	checkFunc("useCPU", func() {
-		useCPU(*duration)
-	})
-	var mu sync.Mutex
-	checkFunc("useCPULocked", func() {
-		mu.Lock()
-		useCPU(*duration)
-		mu.Unlock()
-	})
-}
-
-func checkFunc(kind string, f func()) {
-	log.Printf("Running %s(%s) 100 times, change with --dur", kind, *duration)
-	var ds []time.Duration
-	for i := 0; i < 100; i++ {
-		start := time.Now()
-		f()
-		elapsed := time.Since(start)
-		ds = append(ds, elapsed)
-	}
-	log.Println(ds)
-	sort.Slice(ds, func(i, j int) bool {
-		return ds[i] < ds[j]
-	})
-	log.Println(ds)
-}

coffee/perf.go

@@ -29,15 +29,25 @@ func (arg perfArg) String() string {
 
 const maxSamples = 10000
 
+func utilization() func() (walltime, exectime time.Duration) {
+	var ru1, ru2 syscall.Rusage
+	syscall.Getrusage(syscall.RUSAGE_SELF, &ru1)
+	start := time.Now()
+	return func() (walltime, exectime time.Duration) {
+		syscall.Getrusage(syscall.RUSAGE_SELF, &ru2)
+		return time.Since(start),
+			time.Duration(syscall.TimevalToNsec(ru2.Utime) -
+				syscall.TimevalToNsec(ru1.Utime))
+	}
+}
+
 // perfTest runs f repeatedly until arg.dur elapses, then returns a
 // perfResult containing up to maxSamples uniformly selected
 // durations.  If arg.interval > 0, it specifies the rate at which to
 // attempt requests and increment res.drops on failure.
 func perfTest(arg perfArg, f func()) (res perfResult) {
 	// Pipeline: request generator -> workers -> sampler
-	var ru1, ru2 syscall.Rusage
-	syscall.Getrusage(syscall.RUSAGE_SELF, &ru1)
-	start := time.Now()
+	timings := utilization()
 
 	// Generate requests until arg.dur elapses
 	stop := time.NewTimer(arg.dur)
@@ -109,10 +119,7 @@ func perfTest(arg perfArg, f func()) (res perfResult) {
 			res.samples[j] = elapsed
 		}
 	}
-	syscall.Getrusage(syscall.RUSAGE_SELF, &ru2)
-	res.exectime = time.Duration(syscall.TimevalToNsec(ru2.Utime) -
-		syscall.TimevalToNsec(ru1.Utime))
-	res.walltime = time.Since(start)
+	res.walltime, res.exectime = timings()
 	return
 }