README.md 1.5 KB
Gache notions
Basic idea
Like Memcached, plus...
- Usability:
- True FLUSHALL
- Single process for multiple bins
- Management
- Complete locking dump/restore
- Snapshots
- Tag support
- Pluggable storage
- Journaling
- Write-back/write-through replication
- Chained storage (fast → slow)
But probably slower overall, just more convenient.
Components
- Protocol handling (FSMs)
- Application: Memcache protocol proper
- Presentation: ASCII / Binary
- Transport:
- TCP with persistent connections
- TCP without persistent connections
- UDP
- raw socketpair (stdin/stdout)
- Readline equivalence for ASCII presentation interactions
- Storage
- Pluggable storage
- Journaling
- Storage engines
- Memory
- Memcached, for use as a debugging proxy in front of a standard instance
- Others ?
- Memory
- Main memory allocation
- Slab allocator
- Reporting
- Background expiration lurker
Memory allocation
Memcache slabs model
- http://www.mikeperham.com/2009/06/22/slabs-pages-chunks-and-memcached/ (2009)
- Older versions of memcached used slabs sized based on powers of two, so you'd have a 1KB slab, 2KB slab, 4KB slab, ..., all the way to 1MB.
- Newer (2006: 1.2.0-RC1 ?) versions use 1.25^n for the chunk size
- Allocate slabs for elements of a given size range ("chunks")
- Slabs are made of fixed-size (1MB) pages, split according to the chunk size
- Slab chunk sizes are in a geometric progression: (1 + x)^n