From d3fef6db20596f76d370d9374d966a40f2a42c20 Mon Sep 17 00:00:00 2001
From: Noah Treuhaft <noah.treuhaft@gmail.com>
Date: Fri, 5 Apr 2024 18:48:16 -0400
Subject: [PATCH] Buffer zngio.scanner.workerCh for more concurrency (#5103)

Tracing with package runtime/trace shows the scanner.start and
worker.run goroutines block frequently on the workerCh channel.  Add
buffering to workerCH to reduce blocking and increase concurrency.

When scanning a 4 GB ZNG file containing Zeek logs, this yields a 1.1X
speedup on my 10-core machine.
---
 zio/zngio/scanner.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/zio/zngio/scanner.go b/zio/zngio/scanner.go
index c5d9d55c9a..3c29e65173 100644
--- a/zio/zngio/scanner.go
+++ b/zio/zngio/scanner.go
@@ -40,7 +40,7 @@ func newScanner(ctx context.Context, zctx *zed.Context, r io.Reader, filter zbuf
 			maxSize: opts.Max,
 		},
 		validate:   opts.Validate,
-		workerCh:   make(chan *worker),
+		workerCh:   make(chan *worker, opts.Threads+1),
 		resultChCh: make(chan chan op.Result, opts.Threads+1),
 	}
 	for i := 0; i < opts.Threads; i++ {