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callcount

io.Copy

standard library

The 208th most-called standard-library function by production calls. Called 36,899 times across 852 modules; 4,737 of those run outside tests and generated code.

All of io → Docs on pkg.go.dev ↗

prod calls
4,737
non-test, non-generated
all calls
36,899
total callsites
modules
852
distinct callers
in loop
11%
of prod calls
in tests
6%
2,308 calls
resolved
100%
to a known target

resolution mix

How each call resolves

How each call was attributed. Only resolved kinds, where the target function is known, count toward the ranking. Interface dispatch and unresolved receivers are reported separately and never guessed. Read the taxonomy →

  • Package function100%A direct call to an exported package function, resolved by type.

estimate

Experimental

Estimated relative cost

Roughly 0.00× the estimated relative cost of fmt.Sprintf . Benchmarked at 5.39 ns/op × 4,737 production calls, normalized so fmt.Sprintf = 1.0.

This is not dollars and not a verdict. Per-op time depends heavily on inputs (argument sizes, contention, patterns), the benchmark ran on a single machine (darwin/arm64 (Apple Silicon), go1.26.0), and static call counts are not runtime frequency. How this is estimated →

who calls this

Notable callers

Production calls into Copy from notable Go projects. Open one on the map to see what else it hammers.

where it's called

Callsites in the wild

12 representative callsites of 36,899, prioritizing in-loop and non-test usage. We link to source, never display it.

Copy · 12 of 36,899 callsites

top callers

The modules that reach for it

The modules that call Copy most in this snapshot.

  • github.com/aws/aws-sdk-go-v2/service/ec22,3026%
  • github.com/aws/aws-sdk-go-v2/service/glue1,2863%
  • github.com/aws/aws-sdk-go-v2/service/rds1,0723%
  • github.com/aws/aws-sdk-go-v2/service/iot1,0053%
  • github.com/aws/aws-sdk-go-v2/service/redshift9813%

siblings

More from io

The other most-called functions in this package. See all →