Add perf exporter (#1274)

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>

vendor/github.com/hodgesds/perf-utils/README.md

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+# Perf
+[![GoDoc](https://godoc.org/github.com/hodgesds/perf-utils?status.svg)](https://godoc.org/github.com/hodgesds/perf-utils)
+
+This package is a go library for interacting with the `perf` subsystem in
+Linux. It allows you to do things like see how many CPU instructions a function
+takes, profile a process for various hardware events, and other interesting
+things. The library is by no means finalized and should be considered pre-alpha
+at best.
+
+# Use Cases
+A majority of the utility methods in this package should only be used for
+testing and/or debugging performance issues. Due to the nature of the go
+runtime profiling on the goroutine level is extremely tricky, with the
+exception of a long running worker goroutine locked to an OS thread. Eventually
+this library could be used to implement many of the features of `perf` but in
+accessible via Go directly.
+
+## Caveats
+* Some utility functions will call
+  [`runtime.LockOSThread`](https://golang.org/pkg/runtime/#LockOSThread) for
+  you, they will also unlock the thread after profiling. ***Note*** using these
+  utility functions will incur significant overhead.
+* Overflow handling is not implemented.
+
+# Setup
+Most likely you will need to tweak some system settings unless you are running as root. From `man perf_event_open`:
+
+```
+   perf_event related configuration files
+       Files in /proc/sys/kernel/
+
+           /proc/sys/kernel/perf_event_paranoid
+                  The perf_event_paranoid file can be set to restrict access to the performance counters.
+
+                  2   allow only user-space measurements (default since Linux 4.6).
+                  1   allow both kernel and user measurements (default before Linux 4.6).
+                  0   allow access to CPU-specific data but not raw tracepoint samples.
+                  -1  no restrictions.
+
+                  The existence of the perf_event_paranoid file is the official method for determining if a kernel supports perf_event_open().
+
+           /proc/sys/kernel/perf_event_max_sample_rate
+                  This sets the maximum sample rate.  Setting this too high can allow users to sample at a rate that impacts overall machine performance and potentially lock up the machine.  The default value is 100000  (samples  per
+                  second).
+
+           /proc/sys/kernel/perf_event_max_stack
+                  This file sets the maximum depth of stack frame entries reported when generating a call trace.
+
+           /proc/sys/kernel/perf_event_mlock_kb
+                  Maximum number of pages an unprivileged user can mlock(2).  The default is 516 (kB).
+
+```
+
+# Example
+Say you wanted to see how many CPU instructions a particular function took:
+
+```
+package main
+
+import (
+	"fmt"
+	"log"
+	"github.com/hodgesds/perf-utils"
+)
+
+func foo() error {
+	var total int
+	for i:=0;i<1000;i++ {
+		total++
+	}
+	return nil
+}
+
+func main() {
+	profileValue, err := perf.CPUInstructions(foo)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("CPU instructions: %+v\n", profileValue)
+}
+```
+
+# Benchmarks
+To profile a single function call there is an overhead of ~0.4ms.
+
+```
+$ go test  -bench=BenchmarkCPUCycles .
+goos: linux
+goarch: amd64
+pkg: github.com/hodgesds/perf-utils
+BenchmarkCPUCycles-8        3000            397924 ns/op              32 B/op          1 allocs/op
+PASS
+ok      github.com/hodgesds/perf-utils  1.255s
+```
+
+The `Profiler` interface has low overhead and suitable for many use cases:
+
+```
+$ go test  -bench=BenchmarkProfiler .
+goos: linux
+goarch: amd64
+pkg: github.com/hodgesds/perf-utils
+BenchmarkProfiler-8      3000000               488 ns/op              32 B/op          1 allocs/op
+PASS
+ok      github.com/hodgesds/perf-utils  1.981s
+```
+
+# BPF Support
+BPF is supported by using the `BPFProfiler` which is available via the
+`ProfileTracepoint` function. To use BPF you need to create the BPF program and
+then call `AttachBPF` with the file descriptor of the BPF program. This is not
+well tested so use at your own peril.
+
+# Misc
+Originally I set out to use `go generate` to build Go structs that were
+compatible with perf, I found a really good
+[article](https://utcc.utoronto.ca/~cks/space/blog/programming/GoCGoCompatibleStructs)
+on how to do so. Eventually, after digging through some of the `/x/sys/unix`
+code I found pretty much what I was needed. However, I think if you are
+interested in interacting with the kernel it is a worthwhile read.