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OpSys Def 2

Definitions for Operating Systems' Exam 2

monitor lock plus a condition variable
lock provides mutual exclusion to shared data
condition variable provides a queue for waiting threads inside a critical section
deadlock threads are waiting for resources with circular dependencies
non-preemptable resource cannot be taken away from its current thread without failing the computation
preemptable resource can be resolved by reallocation of resources
starvation a thread is waiting indefinitely
checkpointing taking snapshots of system states from time to time in order to recover from failures or bugs
interprocess communication (IPC) the process by which processes communicate among address spaces
system call a user process asks the OS to do something on the processes behalf
segment a logically contiguous memory region
External Fragmentation memory is wasted because the available memory is not contiguous for allocation
internal fragmentation allocated pages are not fully used
translation lookaside buffers (TLB) Recently translated memory addresses are stored here for short-term reuse
Caching Stores copies of data at places that can be accessed more quickly than it would take to access the original data.
temporal locality recently referenced locations are more likely to be referenced again soon
spatial locality referenced locations tend to be clustered
cache pollution a process loads data into CPU cache unnecessarily, thus causing other needed data to be evicted from the cache into lower levels of the memory hierarchy, potentially all the way down to main memory, degrading performance
virtually addressed cache takes place between the CPU and the translation table
physically addressed cache takes place between the translation tables and the main memory
Demand paging allows pages that are referenced actively to be loaded into memory
Belady's anomaly increasing the memory size actually results in more page faults
thrashing occurs when memory is overcomitted. pages are needed but are tossed out to make room for new pages.
working set pages that were referenced in the previous T seconds. As T -> infinity, the __________ -> the size of the entire process.
polling cpu repeatedly checks the status of a device for exchanging data
Interrupts when a device is read for use, inform the cpu via ___________
direct memory access (DMA) uses an additional controller to perform data movements
double buffering uses two buffers. When one is being used, the other is being filled
device controller converts between serial bit stream and block of bytes
device driver os component that is responsible for hiding the complexity of an I/O device
memory-mapped i/o no distinction is made between device addresses and memory addresses. devices can be accessed the same way as normal memory.
disk platter coated with magnetic materials for recording
disk arm moves a comb of disk heads
tracks each disk platter is divided into concentric tracks
sector smallest unit of disk storage.
cylinder all tracks with a given disk arm position
zone what the cylinder is further divided into
zone-bit recording zones near the edge store more information
track skew starting position of each track is slightly off.
thermo-calibrations performed to account for changes of radius due to termperature changes
seek time time to position the disk heads
rotational latency time to rotate the target sector to underneath the head
Created by: ejs09f