What does allocs/op and B/op mean in go benchmark?

Question

When I run my benchmarks with go test -v -bench=. -benchmem, I see the following results.

f1     10000        120860 ns/op        2433 B/op         28 allocs/op f2     10000        120288 ns/op        2288 B/op         26 allocs/op 

Based on my understanding:

1. 10000 is the number of iterations for i := 0; i < b.N; i++ {.
2. XXX ns/op is approximate time it took for one iteration to complete

But even after reading the docs, I can not find out what B/op and allocs/op mean.

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My guess is that allocs/op has something to do with garbage collection and memory allocation (the less the better).

Can anyone give a nice explanation of the meaning of these values. Also it would be nice to know why do the go up and main steps to reduce them (I realize this is test specific, but may be there are some universal hints that work in many cases)

Answer 1

allocs/op means how many distinct memory allocations occurred per op (single iteration).

B/op is how many bytes were allocated per op.