Merge ChangeSet@1.10: Documentation about flist scalabilityTODO

[rsync/rsync.git] / TODO

diff --git a/TODO b/TODO
index 75d4e56..456cd7b 100644 (file)
--- a/TODO
+++ b/TODO
@@ -40,10 +40,51 @@ Performance
   start, which makes us use a lot of memory and also not pipeline
   network access as much as we could.
 
   start, which makes us use a lot of memory and also not pipeline
   network access as much as we could.
 

+  We need to be careful of duplicate names getting into the file list.
+  See clean_flist().  This could happen if multiple arguments include
+  the same file.  Bad.
+
+  I think duplicates are only a problem if they're both flowing
+  through the pipeline at the same time.  For example we might have
+  updated the first occurrence after reading the checksums for the
+  second.  So possibly we just need to make sure that we don't have
+  both in the pipeline at the same time.  
+
+  Possibly if we did one directory at a time that would be sufficient.
+
+  Alternatively we could pre-process the arguments to make sure no
+  duplicates will ever be inserted.  There could be some bad cases
+  when we're collapsing symlinks.
+
+  We could have a hash table.
+
+  The root of the problem is that we do not want more than one file
+  list entry referring to the same file.  At first glance there are
+  several ways this could happen: symlinks, hardlinks, and repeated
+  names on the command line.
+
+  If names are repeated on the command line, they may be present in
+  different forms, perhaps by traversing directory paths in different
+  ways, traversing paths including symlinks.  Also we need to allow
+  for expansion of globs by rsync.
+
+  At the moment, clean_flist() requires having the entire file list in
+  memory.  Duplicate names are detected just by a string comparison.
+
+  We don't need to worry about hard links causing duplicates because
+  files are never updated in place.  Similarly for symlinks.
+
+  I think even if we're using a different symlink mode we don't need
+  to worry.
+

 Memory accounting
 
   At exit, show how much memory was used for the file list, etc.
 
 Memory accounting
 
   At exit, show how much memory was used for the file list, etc.
 

+  Also we do a wierd exponential-growth allocation in flist.c.  I'm
+  not sure this makes sense with modern mallocs.  At any rate it will
+  make us allocate a huge amount of memory for large file lists.
+

 Hard-link handling
 
   At the moment hardlink handling is very expensive, so it's off by
 Hard-link handling
 
   At the moment hardlink handling is very expensive, so it's off by


@@ -215,8 +256,6 @@ SIGHUP
 
 hang/timeout friendliness
 
 
 hang/timeout friendliness
 

-  On 
-

 verbose output
   
   Indicate whether files are new, updated, or deleted
 verbose output
   
   Indicate whether files are new, updated, or deleted


@@ -238,3 +277,4 @@ rsyncsh
    current host, directory and so on.  We can probably even do
    completion of remote filenames.
 
    current host, directory and so on.  We can probably even do
    completion of remote filenames.
 

+%K%