RedisConf17 - Rax, Listpack and Safe Contexts
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RedisConf17 breakout session by @antirez
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RedisConf17 - Rax, Listpack and Safe Contexts
- 1. Rax, Listpack and safe contexts @antirez
- 2. RAX Redis radix tree implementation
- 4. HDR a b c a-ptr b-ptr c-ptr val-ptr
- 5. Rax facts • 2600 lines of code • Less memory used • Faster than dict.c for most use cases • Ordered! Powerful iterators • 100% fuzz tested
- 6. Rax usages • Cluster key <-> slots tracking (done in 4.0) • Streams data structure (4.2) • Memory efficient Hashes and Sets (4.2) • No longer double encoded! o/ • Main dictionary? Expires?
- 7. Listpack
- 9. entry Main problem… entry entry entry
- 10. prev-len entry Ziplist encoding prev-len entry
- 13. Listpack facts • We have a specification! By Yuval, Oran and me • 1/3 the source code size of ziplist :-) • More memory efficient for Redis data model • work in progress (alpha published) • TODO: 100% fuzz testing
- 15. TSC: what we had • blocking commands in modules • RedisModule_UnblockClient() from thread • No Redis Modules API from threads :-(
- 16. Inside the event loop Redis event loop processing commands
- 17. release-GIL(); Inside the event loop acquire-GIL(); Redis event loop processing commands
- 18. Non blocking KEYS *
- 19. do { RedisModule_ThreadSafeContextLock(ctx); RedisModuleCallReply *reply = RedisModule_Call(ctx, "SCAN","l",(long long)cursor); RedisModule_ThreadSafeContextUnlock(ctx); … }
- 20. /* Note: no context lock to reply. */ do { … for (size_t j = 0; j < items; j++) { RedisModuleCallReply *ele = …; RedisModule_ReplyWithCallReply(ctx,ele); } }
- 22. Replies #2 Context fake client k1 k2 k3 … Real client bl a
- 23. Replies #3 Context fake client k1 k2 k3 … Real client bl a O(1) operation
- 24. Future
- 25. Modules threading future • Key-locking • read-write locks • Automatic blocking of clients accessing busy keys • No need for data structures-level locks
- 26. Thank You Salvatore Sanfilippo Redis Labs Tweet me at @antirez