From 5fb74fc13853b950b5102ef26d665db97f4838fd Mon Sep 17 00:00:00 2001
From: =?utf8?q?Martin=20M=C3=B6hrmann?= <moehrmann@google.com>
Date: Mon, 10 Jun 2019 12:56:59 +0200
Subject: [PATCH] runtime: reduce allocations when building pprof LabelSet
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Pre-allocate the slice of labels with enough capacity
to avoid growslice calls.

Change-Id: I89db59ac722c03b0202e042d1f707bb041e0999f
Reviewed-on: https://go-review.googlesource.com/c/go/+/181517
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
---
 src/runtime/pprof/label.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/runtime/pprof/label.go b/src/runtime/pprof/label.go
index 20f9cdbae6..2d92ef7e8a 100644
--- a/src/runtime/pprof/label.go
+++ b/src/runtime/pprof/label.go
@@ -60,11 +60,11 @@ func Labels(args ...string) LabelSet {
 	if len(args)%2 != 0 {
 		panic("uneven number of arguments to pprof.Labels")
 	}
-	labels := LabelSet{}
+	list := make([]label, 0, len(args)/2)
 	for i := 0; i+1 < len(args); i += 2 {
-		labels.list = append(labels.list, label{key: args[i], value: args[i+1]})
+		list = append(list, label{key: args[i], value: args[i+1]})
 	}
-	return labels
+	return LabelSet{list: list}
 }
 
 // Label returns the value of the label with the given key on ctx, and a boolean indicating
-- 
2.50.0