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 744c0b28ee9bbc64e2b6ac552ece511243085e0d..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::        
 
 @menu
 * Project 4 Background::        

+* Project 4 Suggested Order of Implementation::  

 * Project 4 Requirements::      
 * Project 4 FAQ::               
 @end menu
 * 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}.
 
 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
 
 @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.
 
 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.
 
 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.


@@ -311,11 +340,8 @@ blocks back to disk.  The cache should also be written back to disk in
 @func{filesys_done}, so that halting Pintos flushes the cache.
 
 If you have @func{timer_sleep} from the first project working, write-behind is
 @func{filesys_done}, so that halting Pintos flushes the cache.
 
 If you have @func{timer_sleep} from the first project working, write-behind is

-an excellent application.  If you're still using the base
-implementation of @func{timer_sleep}, be aware that it busy-waits, which
-is not acceptable here (or elsewhere).  If @func{timer_sleep}'s delays seem too
-short or too long, reread the explanation of the @option{-r} option to
-@command{pintos} (@pxref{Debugging versus Testing}).
+an excellent application.  Otherwise, you may implement a less general
+facility, but make sure that it does not exhibit busy-waiting.

 
 You should also implement @dfn{read-ahead}, that is,
 automatically fetch the next block of a file
 
 You should also implement @dfn{read-ahead}, that is,
 automatically fetch the next block of a file


@@ -368,6 +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.
 
 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
 
 @node Project 4 FAQ
 @section FAQ