ydb/library/cpp/yt/system/cpu_id.cpp, branch CLI_2.32.0Mirror of YDB github reposhttps://code.mastervirt.ru/ydb/atom?h=CLI_2.32.02026-06-15T08:32:51ZMake library/cpp/yt/rseq a Linux-only dependency of library/cpp/yt/system2026-06-15T08:32:51Zbabenkobabenko@yandex-team.com2026-06-15T08:13:32Zurn:sha1:12be02b42fc24cf7bd990d56da8cf8908a35db2d
Make library/cpp/yt/rseq a Linux-only dependency of library/cpp/yt/system
commit_hash:7d6f5e738658447529440425b55b2891f6664d81
Add library/cpp/yt/rseq: NYT::GetCurrentCpuId() via Linux rseq2026-06-13T22:35:19Zbabenkobabenko@yandex-team.com2026-06-13T22:15:56Zurn:sha1:450b2fac082943e2029b3390c99501c365795d64
Self-contained current-CPU-id reader backed by Linux **rseq** (restartable
sequences), with **no third-party dependency** (no librseq):
* The rseq ABI is hand-defined; the calling thread is registered lazily via the
rseq syscall.
* Fast path is a single inlined, **branch-free** thread-local read. The offset
always points at a readable `cpu_id` -- the glibc-owned area when glibc registers
rseq (>= 2.35, via the weak `__rseq_offset`/`__rseq_size`), otherwise our own
area -- so an unregistered thread reads `-1` and routes to the slow path.
* Falls back to `sched_getcpu()` (Linux) or `0` (darwin/windows). Works on glibc
**and musl** alike (librseq does not build on musl).
Fiber-TLS contract: the inlined read must be reached only via a non-inlinable,
fiber-switch-free frame (a virtual call or `YT_PREVENT_TLS_CACHING`).
#### Benchmark -- cost of one cpu-id read
| source | time / call |
|---|---|
| `GetCurrentCpuId()` (rseq) | **0.34 ns** |
| `sched_getcpu()` (vDSO) | 3.5 ns |
| `rdtscp` (what `TTscp::Get()` does) | 23 ns |
This is an alternative to the librseq-based review/13886037 -- same speed, but no
contrib dependency and it also covers musl. The unit test pins to each allowed CPU
and asserts the reported id matches.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
commit_hash:09d282c2f48755836b1cd68cedbffc3c6a662eed