internal/pkg: move output buffer to reader

This side is the read end of a pipe and buffering reads from it ended up performing better than buffering one half of the TeeReader (which already goes through the kernel page cache anyway).

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/exec.go

@@ -440,28 +440,23 @@ func (a *execArtifact) cure(f *FContext, hostNet bool) (err error) {
 			}
 		}()
 
-		bw := f.cache.getWriter(status)
+		brStdout, brStderr := f.cache.getReader(stdout), f.cache.getReader(stderr)
 		stdoutDone, stderrDone := make(chan struct{}), make(chan struct{})
 		go scanVerbose(
 			msg, cancel, stdoutDone,
 			"("+a.name+":1)",
-			io.TeeReader(stdout, bw),
+			io.TeeReader(brStdout, status),
 		)
 		go scanVerbose(
 			msg, cancel, stderrDone,
 			"("+a.name+":2)",
-			io.TeeReader(stderr, bw),
+			io.TeeReader(brStderr, status),
 		)
 		defer func() {
 			<-stdoutDone
 			<-stderrDone
-
-			flushErr := bw.Flush()
-			if err == nil {
-				err = flushErr
-			}
-			f.cache.putWriter(bw)
-
+			f.cache.putReader(brStdout)
+			f.cache.putReader(brStderr)
 		}()
 	} else {
 		z.Stdout, z.Stderr = status, status