Test 2 Flashcards
Name the series of conditions, when occurring in pairs simultaneously, can facilitate the creation of a deadlock.
- Mutual Exclusion
- Hold and Wait
- No Preemption
- Circular Wait
Deadlock condition where only one process at a time can use a resource.
Mutual Exclusion
Deadlock condition where the process holding on resource is waiting to acquire a resource held by another process.
Hold and Wait
Deadlock condition where a resource can be released only by the process holding it after the process has completed its task.
No Preemption
Deadlock condition where a set of waiting process such that P(n-1) is waiting for resource from Pn1, and Pn1 is waiting for P0.
Circular Wait
______ contains the logical address space usable by a process.
Base and Limit Registers
A device that maps virtual addresses to physical addresses.
Memory Management Unit (MMU)
______ allows total physical memory space of processes to exceed available physical memory.
Swapping
A ______ is a fast disk large enough to accommodate copies of all memory images.
Backing Store
______-out, ______-in is a swapping variant for priority based scheduling.
Roll-out, Roll-in
______ occurs when the total required memory space EXISTS to satisfy a request, but it is not contiguous.
External Fragmentation
______ occurs when the allocated memory for a process might be SLIGHTLY LARGER than the requested memory.
Internal Fragmentation
What are the three solutions to the Dynamic Storage Allocation problem?
- First-fit: allocate the first hole that is big enough
- Best-fit: allocate the smallest hole that is big enough
- Worst-fit: allocate the largest hole (requires searching the entire list)
Used to translate logical addresses to physical addresses
Page Table
Sits between Main Memory and the CPU registers.
Cache
A ______ list Maintained to keep track of which frames can be allocated.
Free-frame list
A CPU cache that memory management hardware uses to improve virtual address translation speeds.
Transfer Lookaside Buffer (TLB)
The separation of user logical memory and physical memory.
Virtual Memory
The result from the first time there is a reference to a specific page in virtual memory.
Page Fault
______ paging only brings a page into memory when it is needed.
- could result in a lot of page faults
- can be optimized by loading entire process image to swap space at process load time
Demand Paging
Allows both the parent and child processes to initially share the same pages in memory.
Copy-on-write (COW)
A ______ bit can be used to reduce the overhead of page transfers; only modified pages are written to disk.
Modify (dirty) bit
What are the page replacement algorithms? (3)
- FIFO (first in first out)
- LRU (least recently used)
- Second chance (uses a reference bit; if the bit value is 1, decrement and leave in memory, but if the bit is 0 replace with next page.
Type of allocation that is proportional according to the size of the process.
Fixed Page Allocation
Type of replacement where a process selects a replacement frame from set of all frames.
- one process can take frames from another’
- process execution time can vary greatly
- affords greater throughput
Global Replacement
Type of replacement where a process selects from only its allocated sets of frames.
- more consistent performance
- possible under-utilization of memory
Local Replacement
______ occurs when a process is busy swapping pages in and out of memory, so much so, that minimal work is actually performed.
Thrashing
The time it takes to move the disk arm to the desired cylinder.
Random Access Time
The time it takes for the desired sector to rotate under the disk read head.
Seek Time
A ______ is many hosts attached to many storage units; common in large storage environments.
*storage is made available via LUN masking from specific arrays to specific servers
Storage Area Network (SAN)
(total number of bytes transferred) / (total time between first request and completion of last request)
Bandwidth
What are the sources of Disk I/O requests? (3)
- Operating System
- System Processes
- User Processes
*The Operating System maintains the queue of requests per disk or device.
What are the Disk Scheduling Algorithms? (5)
- FCFS (first come first serve)
- SSTF (shortest seek time first)
- SCAN - arm starts reading at one end and services requests as it moves toward the other end, sweeping back and forth reversing direction.
- CSCAN - similar to SCAN, but instead of reversing direction the arm proceeds back to its original position.
- Look/CLOOK - arm only goes as far as the last request in either direction and reverses immediately.
______ is dividing a disk into sectors that the disk controller can read and write.
*usually 512 bytes of data per sector
Low Level / Physical Formatting
To ______ is to divide a disk into one or more cylinders, each treated as a logical disk.
Partition
______ is basically making/implementing a file system.
Logical Formatting
A Uniform logical view of information storage. The smallest allotment of nameable storage.
*structure is decided by the Operating System and/or program
File
Name all File Attributes
- Name (only information in human readable form)
- Identifier (unique tag, identifies the file within the file system)
- Type
- Size
- Location
- Time, date, and user identification
______ are create, write, read, reposition within file, delete, and truncate.
File Operations
A Global table maintained containing process independent open file information.
Open-file Table
______ mediates access to a file. (shared or exclusive)
- Mandatory - access denied dependent upon the locks held and requested.
- Advisory - process can find the status of locks and decide what to do.
Open File Locking
File Access Methods (2)
- Sequential Access (tape drive model of file)
2. Direct Access (random access / relative access)
The subdivisions of a disk are called ______.
*can be used raw (without a file system) or formatted (with a file system)
Partitions
______ adds the ability to directly share data between users.
Acyclic-graph directories
______ specifies how multiple users are to access a shared file system simultaneously.
Consistency Semantics
A ______ uses the same page cache to cache both memory-mapped pages and ordinary file system I/O to avoid double caching data.
Unified Buffer Cache
A ______ caches pages rather than disk blocks using virtual memory techniques and addresses.
*memory mapped I/O uses page caching, while routine I/O uses buffer disk cache via the file system.
Page Cache
A ______ is a separate section of main memory for frequently used blocks.
Buffer Cache
Type of allocation where each file has its own index block(s) of pointers to its data blocks.
Indexed Allocation
Type of allocation where each file is a linked list of blocks (no external fragmentation).
*locating a block can tax I/O and increase seek times
Linked Allocation
Type of allocation where each file occupies a set of contiguous, or adjacent blocks.
Contiguous Allocation
A ______ table is a linear list with a hash data structure.
Hash Table
A list of file names with pointer to data blocks
Linear List
The ______ partition contains the Operating System and is mounted at boot time.
Root
A _______ Control Block contains details about a volume (total number of blocks, number of free blocks, block size, and free block pointers).
Volume Control Block
A _______ Control Block contains information needed by the system in order to boot an Operating System from a volume.
Boot Control Block
A type of file system that manages metadata information and maintains file control blocks.
Logical File System
A _______ Module understands files, logical addresses, and physical blocks; also responsible for translating logical block number to physical block number.
File Organization Module
A _______ driver controls the physical device; manages I/O devices.
Device Driver
A _______ Control Block is a storage structure consisting of information about a file. (exists per file)
File Control Block
