藉由減少例外處理的途徑
降低 Linux 系統呼叫執行成本
$ whoami
- 洪培軒
- afcidk@NCKU CSIE
例外處理
途徑
成本
- Direct (Mode switch cost)
- Indirect (Processor structure pollution)
FlexSC
Flexible System Call
- OSDI 2010
- 1.4x improvement on MySQL
- 2.0x improvement on Apache
Exception-less syscall
Normal syscall
Exception-less syscall
Syscall page
Syscall Batching
經驗
為什麼回頭看十年前的論文？
- 實驗數據的差異
- 小改變 -> 肉眼可見的結果
為什麼要修改 kernel
- 特別的情境
- 某些不需要的功能
電腦技術的演進
- microarchitecture
- Context switch
插曲
實驗結果
- Syscall batching
- multicore (CMWQ)
- single core (CMWQ)
- single core (WQ)
Syscall batching, multicore execution (CMWQ)
Syscall batching, single core execution (CMWQ)
- flexsc 實作的成本
- flexsc 概念的效能提升
- 處理器的進步
Syscall batching, single core execution (CMWQ)
Syscall batching, single core execution (WQ)
workqueue v.s. CMWQ
難題
current pointer
- getpid
- open/read/write
結論
結果不如預期也不算是壞事
藉由減少例外處理的途徑 降低 Linux 系統呼叫執行成本
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