ipfs/kubo

Block cache lock contention

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#6934 opened on Feb 26, 2020

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exp/experthelp wantedkind/enhancementstatus/readytopic/perf

Description

There is quite a bit of lock contention in the block cache. On the gateways, out of 32 walk threads:

  • 13 were waiting on the disk.
  • 19 were blocked on the cache.
    • 10 trying to add blocks
    • 9 trying to get them.

We're currently using github.com/hashicorp/golang-lru.

Contributor guide

Tech stack
go
Domain
performance
Issue type
performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
Goconcurrencycachinglock contention
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Investigate the lock contention in the block cache by profiling the kubod daemon. Focus on the usage of github.com/hashicorp/golang lru and explore alternative cache implementations or lock free data structures. Analyze the code in the block cache module (likely in the core or blocks package) to identify where Add and Get calls are heavily contested.