Clarify parallelism requirements.

[pintos-anon] / doc / vm.texi

diff --git a/doc/vm.texi b/doc/vm.texi
index 840e506a129586d9c2857f22a86a4325cdfafc01..37b53f766d9f710b8b9ed134846ae7b2abbc6843 100644 (file)
--- a/doc/vm.texi
+++ b/doc/vm.texi
@@ -316,12 +316,12 @@ Some way of translating in software from virtual page frames to
 physical page frames.  Pintos provides a hash table that you may find
 useful for this purpose (@pxref{Hash Table}).
 
-It is possible to do this translation without adding a new data
-structure, by modifying the code in @file{userprog/pagedir.c}.  However,
-if you do that you'll need to carefully study and understand section
-3.7, ``Page Translation Using 32-Bit Physical Addressing,'' in
-@bibref{IA32-v3a}, and in practice it is probably easier to add a new
-data structure.
+You don't strictly need a new data structure for this.  You could
+instead modify the code in @file{userprog/pagedir.c}.  If you do that
+you'll need to thoroughly understand how 80@var{x}86 page tables work
+by, e.g.,@: studying section 3.7, ``Page Translation Using 32-Bit
+Physical Addressing,'' in @bibref{IA32-v3a}.  In practice, most groups
+use a separate data structure.
 
 @item
 Some way of finding a page on disk (in a file or in swap) if it is not
@@ -420,11 +420,10 @@ Bits}) to implement an approximation to LRU.  Your algorithm should
 perform at least as well as the ``second chance'' or ``clock''
 algorithm.
 
-Your design should allow for parallelism.  Multiple processes should
-be able to process page faults at once.  If one page fault require
+Your design should allow for parallelism.  If one page fault requires
 I/O, in the meantime processes that do not fault should continue
-executing and other page faults that do not require I/O should be able to
-complete.  These criteria require some synchronization effort.
+executing and other page faults that do not require I/O should be able
+to complete.  These criteria require some synchronization effort.
 
 @node Lazy Loading
 @subsection Lazy Loading
@@ -670,7 +669,7 @@ kernel functions need to obtain memory.
 You can layer some other allocator on top of @func{palloc_get_page} if
 you like, but it should be the underlying mechanism.
 
-Also, you can use the @option{-u} option to @command{pintos} to limit
+Also, you can use the @option{-ul} option to @command{pintos} to limit
 the size of the user pool, which makes it easy to test your VM
 implementation with various user memory sizes.
 
@@ -713,7 +712,7 @@ with the file mapped into your address space, you can directly address
 it like so:
 
 @example
-write (addr, 64, STDOUT_FILENO);
+write (STDOUT_FILENO, addr, 64);
 @end example
 
 Similarly, if you wanted to replace the first byte of the file,