PVM负载敏感性对任务分配的影响

Effect of PVM (Parallel Virtual Machine) Load Sensitivity on Task Distributing

ＰＶＭ负载敏感性对任务分配的影响张博，谷建华，周兴社，武彦萍负载获取与均衡对ＰＶＭ（ＰａｒａｌｌｅｌＶｉｒｔｕａｌＭａｃｈｉｎｅ）任务的分配和系统效率具有重大影响，这也是其它并行分布式计算系统所面临的一个关键技术，但至今为止，还未见到国内外有关ＰＶＭ...

In the May 1994 PVM 3 User's Guide and Referenc Manual, it is mentioned that 'Late rPVM will use the matrices of machine load and rated performance (sp =) to determine themost appropriate hosts.' We analyze the February 1995 PVM source code 3. 3. 7 and find nothing has yet been done on such determination. We now present our preliminary results onthis important problem.The determination of appropriate hosts is the selection of suitable computers to be used in PVM (parallel virtual machine) in order to raise parallel efficiency. We select computers with the aid of the concept of load sensitivity. Using this concept, we find that existing PVM distributes tasks evenly in round - robin fashion without considering what load eachcomputer already carries ; thus synchronizing cooperative tasks is difficult and parallel efficiency is low. This leads naturally to the desirability of improving the load sensitivity of PVM.Our improvement consists of designing and building a load information collector (LIC).LIC allows us: (1) to obtain load information by reading the UNIX special memory devicefile without modifying its operating system and (2) to design a precise load vector scaled tocomputer speed, which helps us to keep track of the load already carried by each computer.With the help of LIC, we modify the pvm -- spawn function to improve the PVM load sensitivity. PVM sends a task distributing request to LIC, LIC sends back an available computer list according to their loads, and PVM finally distributes tasks to the selected computers. Table 1 indicates that the average run time of modified PVM is less by 33%.The environment of Table 1 comprises two SUN4 SPARC2s, three VAX Station3200s and two compatible PC486s connected with Ethernet. The PVM includes one SUN and three VAXs, VAXI is the master and VAX2 is overloaded.The advantages of the method above are: 1) high transparency without modifying the operating system ;2) low communication cost and high reliability ;3) no computer selection collision ; 4) applicability to later PVM.