Chapter 9: Main Memory Flashcards

Flashcards covering main memory concepts, including address binding, memory-management units, contiguous allocation, paging, and page table structures from Silberschatz Chapter 9.

Main memory and __________ are the only storage that the CPU can access directly.

registers

Register access is done in __________ or less, while main memory can take many cycles causing a stall.

$1$ CPU clock

Protection of the logical address space is provided by using a pair of __________ and __________ registers.

base, limit

Loading the base and limit registers are __________ instructions.

privileged

The linker or loader binds relocatable addresses to __________ addresses.

absolute

If memory location is known a priori, __________ can be generated at compile time.

absolute code

Binding is delayed until run time if the process can be moved during execution, requiring hardware support for __________.

address maps

The __________ address is generated by the CPU, while the __________ address is seen by the memory unit.

logical, physical

The __________ is a hardware device that at run time maps virtual to physical addresses.

Memory-Management Unit (MMU)

In a simple MMU scheme, the base register is called the __________ register.

relocation

With __________, a routine is not loaded until it is called, providing better memory-space utilization.

Dynamic Loading

In dynamic linking, a small piece of code called a __________ is used to locate the appropriate memory-resident library routine.

stub

In contiguous allocation, the resident operating system is usually held in __________ memory.

low

The __________-partition allocation method limits the degree of multiprogramming by the number of partitions.

Multiple

In the dynamic storage-allocation problem, __________-fit allocates the smallest hole that is big enough.

Best

__________ fragmentation occurs when total memory space exists to satisfy a request, but it is not contiguous.

External

The 50-percent rule states that for $N$ blocks allocated, __________ blocks are lost to fragmentation.

$$0.5\,N$$

Physical memory is divided into fixed-sized blocks called __________, and logical memory is divided into blocks of the same size called __________.

frames, pages

To translate logical to physical addresses, the OS sets up a __________ for each process.

page table

In the paging address translation scheme, the __________ is used as an index into a page table.

Page number (p)

The __________ points to the page table, and the __________ indicates the size of the page table.

Page-table base register (PTBR), Page-table length register (PTLR)

The two-memory access problem in paging is solved by using a special fast-lookup hardware cache called __________.

translation look-aside buffers (TLBs)

Some TLBs store __________ to uniquely identify each process and provide address-space protection.

address-space identifiers (ASIDs)

The percentage of times that a page number is found in the TLB is known as the __________.

Hit ratio

If memory access takes $10\,ns$ and the TLB hit ratio is $80\%$, the Effective Access Time (EAT) is __________.

$$12\,nanoseconds$$

A __________ bit is attached to each page table entry to signify if the page is in the process's logical address space.

valid-invalid

One copy of __________ code can be shared among processes, which is useful for text editors and compilers.

read-only (reentrant)

A 32-bit logical address space with a page size of $4\,KB$ results in a page table with __________ entries.

$$1\,million$$

The virtual page number is hashed into a table where each element contains the virtual page number, the value of the mapped page frame, and a __________.

pointer to the next element

An __________ page table has one entry for each real page of memory, decreasing memory needed but increasing search time.

inverted

In priority-based scheduling, a lower-priority process is swapped out so a higher-priority process can be loaded, a process called __________.

Roll out, roll in