Operating Systems - Tutorial 2 & 16

Review Basics Allocation Policies Data Structures Segmentation & PagingOperating SystemsTutorial 2 & 16Michael Tänzeros-tut@nhng.dehttp://os-tut.nhng.deCalendar Week 51OS-Tutorial – Week 51 Michael TänzerReview Basics Allocation Policies Data Structures Segmentation & PagingOutline1 Review2 Memory Management Basics3 Memory Allocation Policies4 Memory Management Data Structures5 Segmentation & PagingPagingSegmentation and PagingOS-Tutorial – Week 51 Michael TänzerReview Basics Allocation Policies Data Structures Segmentation & PagingTrue or FalseIf the system is in a safe state all resource requests fromexisting processes which don’t exceed their maximum canbe granted and still no deadlock can occurA circle in a WFG indicates a deadlockBounded waiting is a necessary condition for a deadlockOS-Tutorial – Week 51 Michael TänzerReview Basics Allocation Policies Data Structures Segmentation & PagingExternal vs. internal fragmentationInternal fragmentationApplication gets more memory than neededCan’t be avoided when using fixed size allocation units(pages)Internal fragmentation< page size (on average ½ pagesize)External fragmentationUsed memory contains holes that may be too small tosatisfy an incoming request although on the whole there’senough space) Need to defragment memory to close holesCurrently unusable memory is called externalfragmentationOS-Tutorial – Week 51 Michael TänzerReview Basics Allocation Policies Data Structures ...