L52-core-static-method-host.md

Static strings for method and host for the input to grpc_channel_register_call()

• Author(s): Soheil Hassas Yeganeh
• Approver: vjpai, yashykt
• Status: Approved
• Implemented in: core
• Last updated: 2019-06-05
• Discussion at: https://groups.google.com/forum/#!topic/grpc-io/iYwUVQKU-OU

Abstract

This proposal proposes a requirement to only accept static strings (i.e., kept alive while gRPC is running) for method and host as the arguments to grpc_channel_register_call().

This change requires a major bump of gRPC version.

Background

For pre-registering, method and host are pre-registered on channels using grpc_channel_register_call(). Although no user that we are aware of uses non-static strings for method and host, we have to conservatively intern the strings since grpc_channel_register_call() is not clear about the ownership and life-time of method and host. Interning method and host results in unnecessary ref-counting and cache-line contention for every single call. This can be eliminated by making them static.

Proposal

Require static string for the method and host arguments to grpc_channel_register_call(). That is the method and host strings must be kept valid while the server is up.

Rationale

method and host are reffed for every call. Doing an atomic fetch-add per call is quite expensive, and truly unnecessary since the strings can easily be kept alive while the server is up.

Implementation

This is basically a simple comment update and removing grpc_slice_intern() calls for method and host, as implemented in PR #19263.