中科大操作系统原理与实现课件8_memory2.pdf

《中科大操作系统原理与实现课件8_memory2.pdf》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、操作系统原理与设计第8章MainMemory2陈香兰中国科学技术大学计算机学院2009年09月01日......提纲Paging(分页)BasicMethodHardwaresupportMemoryProtectionSharedPagesStructureofthePageTableHierarchicalPagingHashedPageTablesInvertedPageTables......DiscreteMemoryAllocationIpaging（分页）Iinternalfragmentation

2、mentation（分段）IlogicalIcombinedpaging＆segmentation（段页式）......OutlinePaging(分页)BasicMethodHardwaresupportMemoryProtectionSharedPagesStructureofthePageTableHierarchicalPagingHashedPageTablesInvertedPageTables......PagingIILogicaladdressspaceofaprocesscanbenoncontiguous;proc

3、essisallocatedphysicalmemorywheneverthelatterisavailableIBasicMethod1.Dividephysicalmemoryintofixed-sizedblockscalledframesIsizeispowerof2,between512Band8,192BIPageFrameNumber,PFN:0;1;:::;PFNmax2.DividelogicalmemoryintoblocksofsamesizecalledpagesILogicalFrameNumber,LFN:0;

4、1;:::;LFNmax3.thebackingstoreisalsodividedintofixed-sizedblocksofsamesizeasframes......PagingIIIneedhardwareandsoftwaresupportforpagingIKeeptrackofallfreeframesITorunaprogramofsizenpages,needtofindnfreeframesandloadprogramISetupapagetabletotranslatelogicaltophysicaladdress

5、esforeachprocessIInternalfragmentation

6、=20......I计算页（页框）号和页（页框）内偏移的方法：I地址：AI页（页框）大小：LI页（页框）号p＝A整除LI页（页框）内偏移d＝AmodLI考虑L是2的幂，不妨设为2N，则Ip＝A右移N位，即取A的高(32－N)位Id＝A的低端N位......PagingHardwareILFN(p)+offset(d)!PFN(f)+offset(d)......PagingExample32-bytememoryand4-bytepagesI?readlogicaladdress9?......FreeFramesIISinceOSis

7、managingphysicalmemory,itmustbeawareoftheallocationdetailsofphysicalmemoryIwhichframesareallocatedIwhichframesareavailableIhowmanytotalframesI...Iframetable:oneentryforeachphysicalpageframe......FreeFramesII......OutlinePaging(分页)BasicMethodHardwaresupportMemoryProtectio

8、nSharedPagesStructureofthePageTableHierarchicalPagingHashedPageTablesInvertedPageTables......Hardwaresu