pkg/ipc: don't send program padding to executor

Currently we always send 2MB of data to executor in ipc_simple.go.
Send only what's consumed by the program, and don't send the trailing zeros.
Serialized programs usually take only few KBs.

1 files changed, 4 insertions, 3 deletions

diff --git a/prog/encodingexec.go b/prog/encodingexec.go
index b2b173bbe..e45ba1192 100644
--- a/prog/encodingexec.go
+++ b/prog/encodingexec.go
@@ -57,8 +57,9 @@ func (s ByPhysicalAddr) Less(i, j int) bool {
 }
 
 // SerializeForExec serializes program p for execution by process pid into the provided buffer.
+// Returns number of bytes written to the buffer.
 // If the provided buffer is too small for the program an error is returned.
-func (p *Prog) SerializeForExec(buffer []byte, pid int) error {
+func (p *Prog) SerializeForExec(buffer []byte, pid int) (int, error) {
 	if debug {
 		if err := p.validate(); err != nil {
 			panic(fmt.Errorf("serializing invalid program: %v", err))
@@ -193,9 +194,9 @@ func (p *Prog) SerializeForExec(buffer []byte, pid int) error {
 	}
 	w.write(ExecInstrEOF)
 	if w.eof {
-		return fmt.Errorf("provided buffer is too small")
+		return 0, fmt.Errorf("provided buffer is too small")
 	}
-	return nil
+	return len(buffer) - len(w.buf), nil
 }
 
 func (target *Target) physicalAddr(arg Arg) uint64 {