Clarify need for virt-to-phys translation table.

[pintos-anon] / doc / vm.texi

diff --git a/doc/vm.texi b/doc/vm.texi
index 6e5d5a076b281bdb6dd72515e9b2c22b792fbf93..3703a94a5a301c147d55629007d69b6dfa746591 100644 (file)
--- a/doc/vm.texi
+++ b/doc/vm.texi
@@ -316,11 +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
-in @bibref{IA32-v3}, 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
@@ -669,7 +670,7 @@ 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.
 
@@ -712,7 +713,7 @@ 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,