Memcached内存管理

Transcript

1. Memcached ಺ଘ؅ཧ jiangbo$_ @mokeyj Friday, August 31, 12
2. Slab, Page, Chunk, Item Chunk ^ +------------------|------------------------------------------------------------+ | Memory | | | +---------------|---------------------------------------------------------+ | | | +--------|---------------------+ +------------------------------+ | | | | |Page1 +-|---+ +-----+ +-----+ | |Page2 +-----+ +-----+ +-----+ | | | | | Slab |(1M) | 96B | | 68B | | 72B | | |(1M) | 92B | | 76B | | 84B | | | | | | 1 | +-----+ +-----+ +-----+ | | +-----+ +-----+ +-----+ | | | | | +------------------------------+ +------------------------------+ | | | +-------------------------------------------------------------------------+ | | | | +-------------------------------------------------------------------------+ | | | +------------------------------+ +------------------------------+ | | | | |Page1 +------+ +------+ | |Page2 +------+ +-------+ | | | | | Slab | (1M) | 128B | | 120B | | |(1M) | 128B | | 97B | | | | | | 2 | +------+ +------+ | | +------+ +-------+ | | | | | +------------------------------+ +------------------------------+ | | | +-------------------------------------------------------------------------+ | +-------------------------------------------------------------------------------+ Friday, August 31, 12
3. Item +---------------------------------------+ | key-value | cas | suffix | item head | +---------------------------------------+ 实际ଘ์త਺ਾ Item Size= data size + 32bytes item head Friday, August 31, 12
4. Chunk +------------------------------+ | data item | empty space | +------------------------------+ ଘ์਺ਾత࠷খ单ݩ Friday, August 31, 12
5. Page +-------------------------------------+ | chunk1 | chunk2 | chunk3 | chunk4 | +-------------------------------------+ ਃ请࢖༻಺ଘత࠷খۭ间ɼ ᘍ认为1M Friday, August 31, 12
6. Slab +--------------------------------+ | Page1 | Page2 | Page3 | Page4 | +--------------------------------+ ҈chunkେখෆಉ䎞෼ক಺ଘ䎞෼ଟ࿽slabۭ间 Friday, August 31, 12
7. Slabॳ࢝Խ • ࠜਾෆಉతchunk_size䎞෼为ଟ࿽slabۭ间 • ॳ࢝࠷খchunk_sizeʢᘍ认为80=48+32ʣ • ࠜਾfactor҈ൺྫ递⃧ʢᘍ认1.25ʣ ࢀ⻅见 slabs.cதslabs_init() Friday, August 31, 12
8. ਺ਾଘ储 • 计ࢉitemେখɼፙ౸߹㭕తslab • ਗ਼ཧ该slabதత过ظchunk • ຅༗过ظchunkɼ则ਃ请৽ۭ间(slab_alloc) • ਃ请ۭ间ࣦ败ɼ࢖༻LRUஞग़ ࢀ⻅见item.cதdo_item_alloc() Friday, August 31, 12
9. ਃ请Slab • ဓSlotsྻදதਃ请 • ຅༗则ਃ请Ұ࿽Pageత৽ۭ间 • ਃ请ۭ间ੋձઌ൑அslab_reasignɼᘍ认ෆ 䇖启 ࢀ⻅见slabs.cதslab_alloc() Friday, August 31, 12
10. ಺ଘ࿘费 • Item Size <= Chunk Size • Page Size%Chunk Size ? • ቮ෼഑给slabతۭ间ᘍ认ෆճᏅ Friday, August 31, 12
11. Ҋྫ෼ੳ • ఆ⻓长问题导கେྔஞग़ Friday, August 31, 12
12. THX Friday, August 31, 12