all: preallocate slices with known size

[tklauser]

This avoids reallocations in loops, cf. #10056

Found using github.com/alexkohler/prealloc

[tklauser]

test-me-please

[aanm]

Can we add this as a checker?

[tklauser]

Can we add this as a checker?

Will look into it, yes. But there are some cases in which preallocation doesn't make sense, i.e. the slice is rather small and/or the capacity cannot be estimated reliably. Thus the prealloc results need manual inspection, e.g. I left out these:

pkg/datapath/linux/node_addressing.go:39 Consider preallocating addresses
pkg/endpoint/bpf.go:258 Consider preallocating updatedStats
pkg/envoy/server.go:1031 Consider preallocating policies

Not sure how to tell the checker to ignore these cases.

[aanm]

Can we add this as a checker?

Will look into it, yes. But there are some cases in which preallocation doesn't make sense, i.e. the slice is rather small and/or the capacity cannot be estimated reliably. Thus the prealloc results need manual inspection, e.g. I left out these:

pkg/datapath/linux/node_addressing.go:39 Consider preallocating addresses
pkg/endpoint/bpf.go:258 Consider preallocating updatedStats
pkg/envoy/server.go:1031 Consider preallocating policies

Not sure how to tell the checker to ignore these cases.

I guess there isn't a tag to ignore false positives.

[coveralls]

Coverage increased (+0.04%) to 45.546% when pulling 04549f6 on pr/tklauser/prealloc-slices into 5ff7c51 on master.

[tklauser]

I guess there isn't a tag to ignore false positives.

Doesn't look like it 😞

[tklauser]

Found some other cases using the -forloops flag, please have another look.

[tklauser]

test-me-please

[tklauser]

test-me-please