Go Runtime Performance Checkpoint

1. A 20-byte arena allocates 3 bytes, then AllocAligned(5,8). How many bytes remain? Enter one integer.

2. off=2 in an 8-byte arena; n=MaxInt. Which check is safe before adding? Select one answer.

Select one answer.

Form off+n first, then compare it with len(buf) Reject because n > len(buf)-off Convert wrapped off+n to uint after the sum Allow it because n is positive

3. After Reset, a new allocation overwrites bytes referenced by an old slice. What is the bug if an async reader still uses the old slice? Select one answer.

Select one answer.

Reset failed to run the garbage collector The old slice must retain an immutable copy The caller reused the arena generation before its readers finished Slice capacity prevents Reset from reusing bytes

4. A benchmark reduces dst to 1 byte and becomes much faster with 0 allocations. What should be checked first? Select one answer.

Select one answer.

Whether zero allocations prove higher server throughput Whether the CPU now has more cores Whether ns/op is the service p99 Whether it now measures ErrShortBuffer rather than successful handling

5. A Go process exceeds GOMEMLIMIT. Which fact is compatible with the documented control? Select one answer.

Select one answer.

It is a soft runtime memory limit and may be exceeded; it is not a hard RSS cap The runtime must be broken because crossing it is impossible All external allocations must be counted in it It guarantees a container can never run out of memory

6. For GET /echo?msg=x%2Fy in this course subset, what Content-Length does the response body have? Enter one integer.

7. A complete valid request needs more response bytes than dst holds. What should the caller observe? Select one answer.

Select one answer.

Request consumed with a partial response ErrShortBuffer, consumed=0, written=0, dst unchanged A successful zero-length response Consumption through the request line only

8. Caching a 20-byte slice of a 4 MiB backing buffer has zero new allocation at lookup. What can still happen? Select one answer.

Select one answer.

Only20 bytes remain live automatically The GC moves the20 bytes into a smaller object The entire backing buffer remains reachable through the cached slice Zero allocations imply zero retained heap