Benchmark: fix build tags

[lyuxuan]

some syscall and unix package functions/variables are not defined in environments like windows, darwin, etc.

Restrict to linux only.

---

This change is 

[menghanl]

Those are all cpu time related syscalls.
We should move only that function to a separate file, and add build constraints to that file.

Or, since they are all the same function, we should move those to a separate internal/ package.

[menghanl]

Review status: 0 of 7 files reviewed, 2 unresolved discussions (waiting on @lyuxuan and @menghanl)

---

internal/benchmarkutil/benchmarkutil_linux.go, line 21 at r2 (raw file):

 */

package benchmarkutil

Name this package syscall?

---

internal/benchmarkutil/benchmarkutil_linux.go, line 44 at r2 (raw file):

// Getrusage returns the resource usage of current process.
func Getrusage(rusage *Rusage) {

Make this function return *Rusage instead?

---

Comments from Reviewable

[lyuxuan]

Review status: 0 of 7 files reviewed, 2 unresolved discussions (waiting on @menghanl and @lyuxuan)

---

internal/benchmarkutil/benchmarkutil_linux.go, line 21 at r2 (raw file):

Previously, menghanl (Menghan Li) wrote…

Name this package syscall?

both syscall and unix package functions are included here.

---

internal/benchmarkutil/benchmarkutil_linux.go, line 44 at r2 (raw file):

Previously, menghanl (Menghan Li) wrote…

Make this function return *Rusage instead?

done

---

Comments from Reviewable

[menghanl]

Review status: 0 of 7 files reviewed, 2 unresolved discussions (waiting on @menghanl)

---

internal/benchmarkutil/benchmarkutil_linux.go, line 21 at r2 (raw file):

Previously, lyuxuan wrote…

both syscall and unix package functions are included here.

What I was thinking is, this will be the grpc syscall package. Whenever there's a requirement for syscall in grpc, the code should go here.

unix should be considered as part of syscall. (And it's under x/sys)

---

Comments from Reviewable

[menghanl]

Reviewed 1 of 8 files at r2, 6 of 6 files at r4.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @lyuxuan)

---

benchmark/server/main.go, line 35 at r4 (raw file):

	"google.golang.org/grpc/benchmark"
	"google.golang.org/grpc/grpclog"
	grpcsyscall "google.golang.org/grpc/internal/syscall"

Why does this need to be renamed?

---

internal/syscall/syscall_linux.go, line 40 at r4 (raw file):

// Rusage is an alias for syscall.Rusage under linux non-appengine environment.
// TODO(lyuxuan): use type alias after go1.8 is no longer supported.

Nit: I don't think we want to do this.
type alias actually leaks details of how Rusage is implemented, but I think we want to keep that internal to this package.

[lyuxuan]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lyuxuan)

---

benchmark/server/main.go, line 35 at r4 (raw file):

Previously, menghanl (Menghan Li) wrote…

Why does this need to be renamed?

Because we also import syscall.

---

internal/syscall/syscall_linux.go, line 40 at r4 (raw file):

Previously, menghanl (Menghan Li) wrote…

Nit: I don't think we want to do this.
type alias actually leaks details of how Rusage is implemented, but I think we want to keep that internal to this package.

OK.

---

internal/benchmarkutil/benchmarkutil_linux.go, line 21 at r2 (raw file):

Previously, menghanl (Menghan Li) wrote…

What I was thinking is, this will be the grpc syscall package. Whenever there's a requirement for syscall in grpc, the code should go here.

unix should be considered as part of syscall. (And it's under x/sys)

done

[menghanl]

Reviewed 1 of 1 files at r5.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @menghanl)

---

benchmark/server/main.go, line 35 at r4 (raw file):

Previously, lyuxuan wrote…

Because we also import syscall.

Hmm, it shouldn't... syscall should always be guarded: https://go-proverbs.github.io/

It seems syscall.SIGTERM is only defined for unix-like systems. This file might not build on windows.

It's defined here:
https://github.com/golang/go/blob/go1.10/src/syscall/zerrors_linux_amd64.go#L1365

But not on windows:
https://github.com/golang/go/blob/go1.10/src/syscall/zerrors_windows.go