Optimizing the Copy-on-Write Mechanism of Docker by Dynamic Prefetching  

作　　者：Yan Jiang Wei Liu Xuanhua Shi Weizhong Qiang 

机构地区：[1]National Engineering Research Center for Big Data Technology and System,Services Computing Technology and System Lab,Huazhong University of Science and Technology,Wuhan 430074,China

出　　处：《Tsinghua Science and Technology》2021年第3期266-274,共9页清华大学学报（自然科学版（英文版）

基　　金：supported by the National Key Research and Development Program of China(No.2018YFB1003203);the National Natural Science Foundation of China(Nos.61772218 and 61433019);the Outstanding Youth Foundation of Hubei Province(No.2016CFA032);the Chinese Universities Scientific Fund(No.2019kfyRCPY030)。

摘　　要：Docker,as a mainstream container solution,adopts the Copy-on-Write(CoW)mechanism in its storage drivers.This mechanism satisfies the need of different containers to share the same image.However,when a single container performs operations such as modification of an image file,a duplicate is created in the upper readwrite layer,which contributes to the runtime overhead.When the accessed image file is fairly large,this additional overhead becomes non-negligible.Here we present the concept of Dynamic Prefetching Strategy Optimization(DPSO),which optimizes the Co W mechanism for a Docker container on the basis of the dynamic prefetching strategy.At the beginning of the container life cycle,DPSO pre-copies up the image files that are most likely to be copied up later to eliminate the overhead caused by performing this operation during application runtime.The experimental results show that DPSO has an average prefetch accuracy of greater than 78%in complex scenarios and could effectively eliminate the overhead caused by the CoW mechanism.

关 键 词：DOCKER CONTAINER Copy-on-Write(CoW) storage driver prefetch strategy 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]