Avoid unnecessary map allocation when writing progress

jsternberg · tonistiigi · commit 58e3af59d574 · 2023-08-23T10:25:13.000-07:00
`MultiWriter` would create an unnecessary map allocation when the `Write` method was used. The `Write` method would create a progress object with the meta field initialized to the meta field of the writer itself. It then invoked its own `WriteRawProgress` method which would see two maps with the metadata and erroneously believe that they were different and needed to be merged into a single metadata map. Since this map is initialized with the metadata of the writer before `WriteRawProgress` is invoked, this merge was unnecessary and could add a lot of unnecessary memory allocations during a build. This changes the `MultiWriter.Write` method to invoke the private `writeRawProgress` which performs the actual write and avoids the metadata merge. Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com> (cherry picked from commit 4c83fcf)
diff --git a/util/progress/multiwriter.go b/util/progress/multiwriter.go
@@ -65,7 +65,7 @@ func (ps *MultiWriter) Write(id string, v interface{}) error {
 		Sys:       v,
 		meta:      ps.meta,
 	}
-	return ps.WriteRawProgress(p)
+	return ps.writeRawProgress(p)
 }
 
 func (ps *MultiWriter) WriteRawProgress(p *Progress) error {

Original file line number	Diff line number	Diff line change
`@@ -65,7 +65,7 @@ func (ps *MultiWriter) Write(id string, v interface{}) error {`
`65`	`65`	`Sys: v,`
`66`	`66`	`meta: ps.meta,`
`67`	`67`	`}`
`68`		`- return ps.WriteRawProgress(p)`
	`68`	`+ return ps.writeRawProgress(p)`
`69`	`69`	`}`
`70`	`70`
`71`	`71`	`func (ps MultiWriter) WriteRawProgress(p Progress) error {`