- +---------------------------+
- | CS 140 |
+ +---------------------------+
+ | CS 140 |
| PROJECT 3: VIRTUAL MEMORY |
- | DESIGN DOCUMENT |
+ | DESIGN DOCUMENT |
+---------------------------+
---- GROUP ----
>> Please cite any offline or online sources you consulted while
>> preparing your submission, other than the Pintos documentation, course
->> text, and lecture notes.
+>> text, lecture notes, and course staff.
PAGE TABLE MANAGEMENT
=====================
---- DATA STRUCTURES ----
->> Copy here the declaration of each new or changed `struct' or `struct'
->> member, global or static variable, `typedef', or enumeration.
->> Identify the purpose of each in 25 words or less.
+>> A1: Copy here the declaration of each new or changed `struct' or
+>> `struct' member, global or static variable, `typedef', or
+>> enumeration. Identify the purpose of each in 25 words or less.
---- ALGORITHMS ----
->> Describe your code for locating the physical page, if any, that
->> contains the data of a given virtual page.
+>> A2: In a few paragraphs, describe your code for accessing the data
+>> stored in the SPT about a given page.
->> How does your code coordinate accessed and dirty bits between kernel
->> and user virtual addresses that alias a single physical page, or
+>> A3: How does your code coordinate accessed and dirty bits between
+>> kernel and user virtual addresses that alias a single frame, or
>> alternatively how do you avoid the issue?
---- SYNCHRONIZATION ----
->> When two user processes both need a new page frame at the same time,
+>> A4: When two user processes both need a new frame at the same time,
>> how are races avoided?
---- RATIONALE ----
->> Why did you choose the data structure(s) that you did for representing
->> virtual-to-physical mappings?
+>> A5: Why did you choose the data structure(s) that you did for
+>> representing virtual-to-physical mappings?
PAGING TO AND FROM DISK
=======================
---- DATA STRUCTURES ----
->> Copy here the declaration of each new or changed `struct' or `struct'
->> member, global or static variable, `typedef', or enumeration.
->> Identify the purpose of each in 25 words or less.
+>> B1: Copy here the declaration of each new or changed `struct' or
+>> `struct' member, global or static variable, `typedef', or
+>> enumeration. Identify the purpose of each in 25 words or less.
---- ALGORITHMS ----
->> When a physical page frame is required but none is free, some page
->> frame must be evicted. Describe your code for choosing a frame to
->> evict.
+>> B2: When a frame is required but none is free, some frame must be
+>> evicted. Describe your code for choosing a frame to evict.
->> Explain your heuristic for deciding whether a page fault for an
->> invalid virtual address should cause the stack to be extended into the
->> page that faulted.
+>> B3: When a process P obtains a frame that was previously used by a
+>> process Q, how do you adjust the page table (and any other data
+>> structures) to reflect the frame Q no longer has?
----- SYNCHRONIZATION ----
-
->> Explain the basics of your VM synchronization design. In particular,
->> explain how it prevents deadlock. (Refer to the textbook for an
->> explanation of the necessary conditions for deadlock.)
+>> B4: Explain your heuristic for deciding whether a page fault for an
+>> invalid virtual address should cause the stack to be extended into
+>> the page that faulted.
->> A page fault in process P can cause another process Q's page frame to
->> be evicted. How do you ensure that Q cannot access or modify the page
->> during the eviction process? How do you avoid a race between P
->> evicting Q's page frame and Q faulting the page back in?
-
->> Suppose a page fault in process P causes a page to be read from disk.
->> How do you ensure that a second process Q cannot interfere by e.g.
->> attempting to evict the page while it is still being read in?
+---- SYNCHRONIZATION ----
->> Explain how you handle access to paged-out pages that occur during
->> system calls. Do you use page faults to bring in pages (as in user
->> programs), or do you have a mechanism for "locking" pages into
->> physical memory, or do you use some other design? How do you
+>> B5: Explain the basics of your VM synchronization design. In
+>> particular, explain how it prevents deadlock. (Refer to the
+>> textbook for an explanation of the necessary conditions for
+>> deadlock.)
+
+>> B6: A page fault in process P can cause another process Q's frame
+>> to be evicted. How do you ensure that Q cannot access or modify
+>> the page during the eviction process? How do you avoid a race
+>> between P evicting Q's frame and Q faulting the page back in?
+
+>> B7: Suppose a page fault in process P causes a page to be read from
+>> the file system or swap. How do you ensure that a second process Q
+>> cannot interfere by e.g. attempting to evict the frame while it is
+>> still being read in?
+
+>> B8: Explain how you handle access to paged-out pages that occur
+>> during system calls. Do you use page faults to bring in pages (as
+>> in user programs), or do you have a mechanism for "locking" frames
+>> into physical memory, or do you use some other design? How do you
>> gracefully handle attempted accesses to invalid virtual addresses?
---- RATIONALE ----
->> A single lock for the whole VM system would make synchronization easy,
->> but limit parallelism. On the other hand, using many locks
->> complicates synchronization and raises the possibility for deadlock
->> but allows for high parallelism. Explain where your design falls
->> along this continuum and why you chose to design it this way.
+>> B9: A single lock for the whole VM system would make
+>> synchronization easy, but limit parallelism. On the other hand,
+>> using many locks complicates synchronization and raises the
+>> possibility for deadlock but allows for high parallelism. Explain
+>> where your design falls along this continuum and why you chose to
+>> design it this way.
MEMORY MAPPED FILES
===================
---- DATA STRUCTURES ----
->> Copy here the declaration of each new or changed `struct' or `struct'
->> member, global or static variable, `typedef', or enumeration.
->> Identify the purpose of each in 25 words or less.
+>> C1: Copy here the declaration of each new or changed `struct' or
+>> `struct' member, global or static variable, `typedef', or
+>> enumeration. Identify the purpose of each in 25 words or less.
---- ALGORITHMS ----
->> Describe how memory mapped files integrate into your virtual memory
->> subsystem. Explain how the page fault and eviction processes differ
->> for swap pages and other pages.
+>> C2: Describe how memory mapped files integrate into your virtual
+>> memory subsystem. Explain how the page fault and eviction
+>> processes differ between swap pages and other pages.
->> Explain how you determine whether a new file mapping overlaps any
->> existing segment.
+>> C3: Explain how you determine whether a new file mapping overlaps
+>> any existing segment.
---- RATIONALE ----
->> Mappings created with "mmap" have similar semantics to those of data
->> demand-paged from executables, except that "mmap" mappings are written
->> back to their original files, not to swap. This implies that much of
->> their implementation can be shared. Explain why your implementation
->> either does or does not share much of the code for the two situations.
+>> C4: Mappings created with "mmap" have similar semantics to those of
+>> data demand-paged from executables, except that "mmap" mappings are
+>> written back to their original files, not to swap. This implies
+>> that much of their implementation can be shared. Explain why your
+>> implementation either does or does not share much of the code for
+>> the two situations.
SURVEY QUESTIONS
================
projects / pintos-anon / blobdiff