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process: Deduplicate paths in parseMappings() #403

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Merged
rockdaboot merged 1 commit into from
Mar 17, 2025
Merged

process: Deduplicate paths in parseMappings() #403

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11 changes: 10 additions & 1 deletion process/process.go
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,8 @@ func parseMappings(mapsFile io.Reader) ([]Mapping, error) {
}
bufPool.Put(scanBuf)
}()

lastPath := ""
scanner.Buffer(*scanBuf, 8192)
for scanner.Scan() {
var fields [6]string
Expand Down Expand Up @@ -146,7 +148,14 @@ func parseMappings(mapsFile io.Reader) ([]Mapping, error) {
}
} else {
path = trimMappingPath(path)
path = strings.Clone(path)
if path == lastPath {
// Take advantage of the fact that mappings are sorted by path
// and avoid allocating the same string multiple times.
path = lastPath
} else {
Comment on lines +151 to +155
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@florianl florianl Mar 17, 2025

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Can we skip the assignment of path = lastPath if path == lastPath?

Suggested change
if path == lastPath {
// Take advantage of the fact that mappings are sorted by path
// and avoid allocating the same string multiple times.
path = lastPath
} else {
if path != lastPath {

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@rockdaboot rockdaboot Mar 17, 2025

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Can we skip the assignment of path = lastPath if path == lastPath?

No, this is exactly where the de-duplication happens.
path == lastPath compares the string content, and here both contents are at different memory locations. So if the contents are the same, the path = lastPath changes the memory location of path to the already existing lastPath.

path = strings.Clone(path)
lastPath = path
}
}

vaddr := util.HexToUint64(addrs[0])
Expand Down