计算机系 信息处理实验室 Lecture 10 Memory Management(2)

计算机系 信息处理实验室 the Inside of Windows Contents Memory Manager Components Services the Memory Manager Provides System Memory Pools Address Space Layout Address Translation Page Fault Handling Virtual Address Descriptors Working Sets Page Frame Number Database Section Objects

计算机系 信息处理实验室 the Inside of Windows Page Fault Handling Page fault | |  Kernel trap handler | |  Memory manager: fault handler

计算机系 信息处理实验室 the Inside of Windows Page fault conditions Page fault can be caused by a variety of conditions See table 7-14table 7-14

计算机系 信息处理实验室 the Inside of Windows basic invalid PTEs Page file The desired page resides within a paging file. An in-page operation is initiated

计算机系 信息处理实验室 the Inside of Windows basic invalid PTEs Demand zero A page of zeros The pager : zero page list | |  free list | |  standby list PTE format : zeros the page file number and offset in the former format

计算机系 信息处理实验室 the Inside of Windows basic invalid PTEs Transition The desired page is in memory the standby, modified, or modified-no-write list The page is removed from the list and added to the working set

计算机系 信息处理实验室 the Inside of Windows basic invalid PTEs Unknown The PTE is zero, or The page table doesn't yet exist.

计算机系 信息处理实验室 the Inside of Windows Prototype PTEs For shared pages Prototype page table entries Section objects : an array of prototype PTEs First reference: Prototype PTE  real PTE Reference counter in PFN database 0  invalid the shared page

计算机系 信息处理实验室 the Inside of Windows Prototype PTEs Structure of an invalid PTE that points to the prototype PTE States of a shared page Active/valid; transition; modified-no-write; demand zero; page file; mapped file Lazy updating

计算机系 信息处理实验室 the Inside of Windows Two virtual pages (valid/invalid)

计算机系 信息处理实验室 the Inside of Windows In-Paging I/O Reading a file to satisfy a page fault In-page I/O operation Synchronous not interruptible by APC

计算机系 信息处理实验室 the Inside of Windows Collided page faults The currently being in-paged page is faulted by another thread or process A wait operation is issued When the I/O completes, all threads will be satisfied

计算机系 信息处理实验室 the Inside of Windows Page files To store modified pages because of modified page writing 2K supports up to 16 paging files EXPERIMENT Viewing system page files Viewing Page File Usage with Task Manager

计算机系 信息处理实验室 the Inside of Windows Virtual Address Descriptors Lazy evaluation Copy-on-write Demand paging Page table constructing Advantages and disadvantages

计算机系 信息处理实验室 the Inside of Windows Virtual Address Descriptors

计算机系 信息处理实验室 the Inside of Windows EXPERIMENT Viewing Virtual Address Descriptors

计算机系 信息处理实验室 the Inside of Windows Working Sets Working Set A subset of virtual pages resident in physical memory Two types Process working sets System working set

计算机系 信息处理实验室 the Inside of Windows Paging Policies How (or when) paging is performed fetch policy placement policy replacement policy

计算机系 信息处理实验室 the Inside of Windows Fetch policy When Eager-paging (Before needed) Demand-paging (Until needed) 2K Demand-paging + …. to minimize the number of paging I/Os

计算机系 信息处理实验室 the Inside of Windows Page Fault Read Clustering Values Memory Size Cluster Size for Code Pages in Images Cluster Size for Data Pages in Images Cluster Size for All Other Pages < 12 MB MB325 > 19 MB848

计算机系 信息处理实验室 the Inside of Windows Placement policy Where the size of CPU memory caches must be considered to minimize unnecessary thrashing of the cache

计算机系 信息处理实验室 the Inside of Windows Replacement policy Which Which virtual page must be removed from memory to make room for the new page Include LRU FIFO … Global or local

计算机系 信息处理实验室 the Inside of Windows K replacement policy For multiprocessor system a variation of a local FIFO For uniprocessor system Similar to LRU

计算机系 信息处理实验室 the Inside of Windows Working Set Management Default Minimum and Maximum Working Set Sizes To change: SetProcessWorkingSetSize Memory Size Default Minimum Working Set Size (in Pages) Default Maximum Working Set Size (in Pages) Small2045 Medium30145 Large50345 Maximum value must < system value MmMaximumWorkingSetSize

计算机系 信息处理实验室 the Inside of Windows Working set management When paging, it examines the process's working set limits and the amount of free memory When MmAvailablePages <= MmMinimumFreePages Must trimming working set (working set manager is called) Working set manager determines which how many

计算机系 信息处理实验室 the Inside of Windows Working Set-Related System Control Variables VariableValue MmWorkingSetSize-Increment6 MmWorkingSetSize-Expansion20 MmWsExpandThreshold90 MmPagesAboveWsMinimumDynamic MmPagesAboveWsThreshold37 MmWsAdjustThreshold45 MmWsTrimReductionGoal29

计算机系 信息处理实验室 the Inside of Windows EXPERIMENT Viewing Process Working Set Sizes Viewing the Working Set List

计算机系 信息处理实验室 the Inside of Windows Balance Set Manager and Swapper Balance set manager A system thread for Working set expansion and trimming Routine: KeBalanceSetManager Two event 1-second timer expiring Internal working set manager

计算机系 信息处理实验室 the Inside of Windows Balance set manager Every fourth time  wakes up swapper Swapper: routine (KeSwapProcessOrStack) Checks look-aside lists and adjusts their depths Looks for priority boosted threads Calls the working set manager

计算机系 信息处理实验室 the Inside of Windows Swapper Called by Balance set manager Or scheduling code Looks for threads that can be swapped out And swapped in some threads

计算机系 信息处理实验室 the Inside of Windows System Working Set five kinds of pages System cache pages Paged pool Pageable code and data in Ntoskrnl.exe Pageable code and data in device drivers System mapped views (sections mapped at 0xA , such as Win32k.sys)

计算机系 信息处理实验室 the Inside of Windows System Working Set Performance Counters Performance Counter (in Bytes) System Variable (in Pages) Memory: Cache BytesMmSystemCacheWs.WorkingSetSize Memory: Cache Bytes Peak MmSystemCacheWs.Peak Memory: System Cache Resident Bytes MmSystemCachePage Memory: System Code Resident Bytes MmSystemCodePage Memory: System Driver Resident Bytes MmSystemDriverPage Memory: Pool Paged Resident Bytes MmPagedPoolPage

计算机系 信息处理实验室 the Inside of Windows System Working Set Minimum and Maximum Size Memory Size Minimum (in Pages) Maximum (in Pages) Small Medium Large

计算机系 信息处理实验室 the Inside of Windows Page Frame Number Database the page frame number (PFN) database describes the state of each page in physical memory. States include Active/Transition/Standby/Modified/ Modified no-write/Free/Zeroed/Bad The PFN database consists of an array of structures that represent each physical page of memory on the system.

计算机系 信息处理实验室 the Inside of Windows Page tables & PFN database

计算机系 信息处理实验室 the Inside of Windows Page lists in PFN database

计算机系 信息处理实验室 the Inside of Windows EXPERIMENT Viewing the PFN Database

计算机系 信息处理实验室 the Inside of Windows Page List Dynamics state diagram for page frame transitions

计算机系 信息处理实验室 the Inside of Windows EXPERIMENT Viewing Page Fault Behavior

计算机系 信息处理实验室 the Inside of Windows Modified Page Writer writing pages back to disk, include two system threads MiModifiedPageWriter To paging file MiMappedPageWriter To mapped files The modified page writer event is triggered by the number of modified pages > MmModifiedPageMaximum Or MmAvailablePages < MmMinimumFreePages

计算机系 信息处理实验室 the Inside of Windows Modified Page Writer Values Memory SizeModified Page Threshold Retain Modified Pages < 12 MB MB MB >33 MB (special case)

计算机系 信息处理实验室 the Inside of Windows PFN Data Structures The states of a PFN entry

计算机系 信息处理实验室 the Inside of Windows Flags Within PFN Database Entries Modified state Prototype PTE Parity error Read in progress Write in progress Start of nonpaged pool End of nonpaged pool In-page error

计算机系 信息处理实验室 the Inside of Windows Section Objects section object can be mapped to the paging file or to another file on disk. Section objects, like other objects, are allocated and deallocated by the object manager

计算机系 信息处理实验室 the Inside of Windows A section object

计算机系 信息处理实验室 the Inside of Windows Internal section structures

计算机系 信息处理实验室 the Inside of Windows EXPERIMENT Viewing Section Objects Viewing Control Areas