microsoft / microsoft/ntttcp-for-linux
Remove structure slops to reduce cache pressure
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- Dominant language
- C
- Stars
- 426
- Forks
- 108
- PR merge metrics
- No merged PRs in 30d
Description
Many shared structs are ordered in a way that, when built on a LP64 system, will have unused bytes due to alignment. These structs may be reduced by carefully reordering them, and maybe changing certain types of members to something that packs better.
For instance, struct ntttcp_stream_server has a sizeof 144, spanning over 3 cache lines. According to pahole, it could be at least 129, which is 5 bytes over using just 2 cache lines. By changing all the bool elements to a single integer holding flags, this would fit 2 cache lines.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the definition of struct ntttcp_stream_server and other shared structs in the C sources. Build on an LP64 system and inspect layouts with pahole, then identify padding and unused alignment space. Done means the structs use fewer cache lines while preserving their intended fields and behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c
- Domain
- networking, performance
- Issue type
- Refactor
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100