runtime: scavengeOne ignores searchIdx optimization

[mvdan]

// [...]
// searchIdx is the page index to start searching from in ci.
// [...]
func (p *pageAlloc) scavengeOne(ci chunkIdx, searchIdx uint, max uintptr) uintptr {

Yet searchIdx has never been used in the func body, as far as I can see. Is the parameter truly unnecessary and can be removed, or is it a bug that the parameter isn't being used? I found this one via unparam, but it's not a clear one without understanding the context of the function.

cc @mknyszek @prattmic per git blame :)

[mvdan]

Another one nearby: gcmarknewobject does not use its scanSize parameter, but at least that one isn't documented.

[mknyszek]

Ah, that's a mistake, albeit a minor one. It's not a bug, just slightly less efficient. It should be passed to findScavengeCandidate instead of pallocChunkPages-1.

[mknyszek]

The extra argument gcmarknewobject is likely a leftover from the Go 1.18 pacer updates. I believe it was used by the Go 1.17 pacer and when I deleted the branches in Go 1.19 I neglected to delete the parameter.

[mknyszek]

No need to file an issue about gcmarknewobject, I'll just clean that up sometime this cycle.

[mvdan]

Ack, I'll leave both here for you then :)

[gopherbot]

Change https://go.dev/cl/429255 mentions this issue: runtime: use searchIdx in scavengeOne