Note that struct file, struct dir are per-thread.

[pintos-anon] / doc / filesys.texi

diff --git a/doc/filesys.texi b/doc/filesys.texi
index 9075c9a5a3c2f113319b980fb205bba596d00b2a..f245daa48ea1e6d592a86146ddddf9947ca9cffe 100644 (file)
--- a/doc/filesys.texi
+++ b/doc/filesys.texi
@@ -16,6 +16,7 @@ to 5% extra credit if you do enable VM.
 
 @menu
 * Project 4 Background::        
+* Project 4 Suggested Order of Implementation::  
 * Project 4 Requirements::      
 * Project 4 FAQ::               
 @end menu
@@ -108,6 +109,33 @@ out the file system contents is the standard Unix ``tar'' format.  You
 can use the Unix @command{tar} program to examine them.  The tar file
 for test @var{t} is named @file{@var{t}.tar}.
 
+@node Project 4 Suggested Order of Implementation
+@section Suggested Order of Implementation
+
+We suggest implementing the parts of this project in the following
+order to make your job easier:
+
+@enumerate
+@item
+Buffer cache (@pxref{Buffer Cache}).  Implement the buffer cache and
+integrate it into the existing file system.  At this point all the
+tests from project 2 (and project 3, if you're building on it) should
+still pass.
+
+@item
+Extensible files (@pxref{Indexed and Extensible Files}).  After this
+step, your project should pass the file growth tests.
+
+@item
+Subdirectories (@pxref{Subdirectories}).  Afterward, your project
+should pass the directory tests.
+
+@item
+Remaining miscellaneous items.
+@end enumerate
+
+You should think about synchronization throughout.
+
 @node Project 4 Requirements
 @section Requirements
 
@@ -287,11 +315,12 @@ disk.  Otherwise, fetch the block from disk into cache, evicting an
 older entry if necessary.  You are limited to a cache no greater than 64
 sectors in size.
 
-Be sure to choose an intelligent cache replacement algorithm.
-Experiment to see what combination of accessed, dirty, and other
-information results in the best performance, as measured by the number
-of disk accesses.  For example, metadata is generally more valuable to
-cache than data.
+You must implement a cache replacement algorithm that is at least as
+good as the ``clock'' algorithm.  Your algorithm must also account for
+the generally greater value of metadata compared to data.  Experiment
+to see what combination of accessed, dirty, and other information
+results in the best performance, as measured by the number of disk
+accesses.
 
 You can keep a cached copy of the free map permanently in memory if you
 like.  It doesn't have to count against the cache size.
@@ -365,6 +394,10 @@ if B's data is all nonzero bytes, A is not allowed to see any zeros.
 Operations on different directories should take place concurrently.
 Operations on the same directory may wait for one another.
 
+Keep in mind that only data shared by multiple threads needs to be
+synchronized.  In the base file system, @struct{file} and @struct{dir}
+are accessed only by a single thread.
+
 @node Project 4 FAQ
 @section FAQ