'ls' speedup when sorting lots of file names

[Paul Eggert]

This patch causes "ls" to run about 50% faster on my
platform.  I'm running Debian stable x86, with file info
cached in main memory, and with an en_US.UTF-8 locale.  I'm
testing this by using the command "ls bigdir >outfile",
where "bigdir" is a file containing 60895 files with names
"0", "1", "2", ..., "60894".

The downside of the patch is that it uses a bit more main
memory (valgrind reports 5.8% more malloced storage, using
the above test case), but I think it's a worthwhile
tradeoff.

2007-01-28  Paul Eggert  <address@hidden>

        Modify "ls" to sort its data faster, using the new gnulib mpsort
        module rather than qsort.  This is particularly a win in
        environments where strcoll is slow, since mpsort typically calls
        strcoll less often than qsort does.
        * bootstrap.conf (gnulib_modules): Add mpsort.
        * src/ls.c: Include mpsort.h.
        (sorted_file, sorted_file_alloc): New vars, for a new vector of
        pointers to the file info, for speed.
        (clear_files, extract_dirs_from_files, sort_files, print_current_files):
        (print_many_per_line, print_horizontal, print_with_commas):
        (calculate_columns): Set and use new vector.
        (initialize_ordering_vector): New function.

diff --git a/bootstrap.conf b/bootstrap.conf
index b262622..631f2ed 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -53,7 +53,7 @@ gnulib_modules="
        lchmod lchown lib-ignore linebuffer link-follow
        long-options lstat malloc mbswidth md5 memcasecmp mempcpy
        memrchr mkancesdirs mkdir mkdir-p mkstemp mktime modechange
-       mountlist obstack pathmax perl physmem posixtm posixver putenv
+       mountlist mpsort obstack pathmax perl physmem posixtm posixver putenv
        quote quotearg raise readlink readtokens readtokens0 readutmp
        realloc regex rename-dest-slash rmdir rmdir-errno
        root-dev-ino
diff --git a/src/ls.c b/src/ls.c
index 3864ed0..6e610c4 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -93,6 +93,7 @@
 #include "ls.h"
 #include "lstat.h"
 #include "mbswidth.h"
+#include "mpsort.h"
 #include "obstack.h"
 #include "quote.h"
 #include "quotearg.h"
@@ -279,6 +280,11 @@ static size_t nfiles;  /* FIXME: rename this to e.g. 
cwd_n_alloc */
 /* Index of first unused in `files'.  */
 static size_t files_index;  /* FIXME: rename this to e.g. cwd_n_used */

+/* Vector of pointers to files, in proper sorted order, and the number
+   of entries allocated for it.  */
+static void **sorted_file;
+static size_t sorted_file_alloc;
+
 /* When true, in a color listing, color each symlink name according to the
    type of file it points to.  Otherwise, color them according to the `ln'
    directive in LS_COLORS.  Dangling (orphan) symlinks are treated specially,
@@ -2504,8 +2510,9 @@ clear_files (void)

   for (i = 0; i < files_index; i++)
     {
-      free (files[i].name);
-      free (files[i].linkname);
+      struct fileinfo *f = sorted_file[i];
+      free (f->name);
+      free (f->linkname);
     }

   files_index = 0;
@@ -2860,36 +2867,34 @@ extract_dirs_from_files (char const *dirname, bool 
command_line_arg)
   /* Queue the directories last one first, because queueing reverses the
      order.  */
   for (i = files_index; i-- != 0; )
-    if (is_directory (&files[i])
-        && (! ignore_dot_and_dot_dot
-            || ! basename_is_dot_or_dotdot (files[i].name)))
-      {
-       if (!dirname || files[i].name[0] == '/')
-         {
-           queue_directory (files[i].name, files[i].linkname,
-                            command_line_arg);
-         }
-       else
-         {
-           char *name = file_name_concat (dirname, files[i].name, NULL);
-           queue_directory (name, files[i].linkname, command_line_arg);
-           free (name);
-         }
-       if (files[i].filetype == arg_directory)
-         free (files[i].name);
-      }
+    {
+      struct fileinfo *f = sorted_file[i];
+
+      if (is_directory (f)
+         && (! ignore_dot_and_dot_dot
+             || ! basename_is_dot_or_dotdot (f->name)))
+       {
+         if (!dirname || f->name[0] == '/')
+           queue_directory (f->name, f->linkname, command_line_arg);
+         else
+           {
+             char *name = file_name_concat (dirname, f->name, NULL);
+             queue_directory (name, f->linkname, command_line_arg);
+             free (name);
+           }
+         if (f->filetype == arg_directory)
+           free (f->name);
+       }
+    }

   /* Now delete the directories from the table, compacting all the remaining
      entries.  */

   for (i = 0, j = 0; i < files_index; i++)
     {
-      if (files[i].filetype != arg_directory)
-       {
-         if (j < i)
-           files[j] = files[i];
-         ++j;
-       }
+      struct fileinfo *f = sorted_file[i];
+      sorted_file[j] = f;
+      j += (f->filetype != arg_directory);
     }
   files_index = j;
 }
@@ -3113,6 +3118,15 @@ static qsortFunc sort_functions[][2][2][2] =
 verify (ARRAY_CARDINALITY (sort_functions)
        == sort_numtypes + time_numtypes - 1 );

+/* Set up SORTED_FILE to point to the in-use entries in FILES, in order.  */
+
+static void
+initialize_ordering_vector (void)
+{
+  size_t i;
+  for (i = 0; i < files_index; i++)
+    sorted_file[i] = &files[i];
+}

 /* Sort the files now in the table.  */

@@ -3121,6 +3135,15 @@ sort_files (void)
 {
   bool use_strcmp;

+  if (sorted_file_alloc < files_index + files_index / 2)
+    {
+      free (sorted_file);
+      sorted_file = xnmalloc (files_index, 3 * sizeof *sorted_file);
+      sorted_file_alloc = 3 * files_index;
+    }
+
+  initialize_ordering_vector ();
+
   if (sort_type == sort_none)
     return;

@@ -3135,13 +3158,14 @@ sort_files (void)
     {
       use_strcmp = true;
       assert (sort_type != sort_version);
+      initialize_ordering_vector ();
     }

   /* When sort_type == sort_time, use time_type as subindex.  */
-  qsort (files, files_index, sizeof *files,
-         sort_functions[sort_type + (sort_type == sort_time ? time_type : 0)]
-                      [use_strcmp][sort_reverse]
-                       [directories_first]);
+  mpsort ((void const **) sorted_file, files_index,
+         sort_functions[sort_type + (sort_type == sort_time ? time_type : 0)]
+                       [use_strcmp][sort_reverse]
+                       [directories_first]);
 }

 /* List all the files now in the table.  */
@@ -3156,7 +3180,7 @@ print_current_files (void)
     case one_per_line:
       for (i = 0; i < files_index; i++)
        {
-         print_file_name_and_frills (files + i);
+         print_file_name_and_frills (sorted_file[i]);
          putchar ('\n');
        }
       break;
@@ -3176,7 +3200,7 @@ print_current_files (void)
     case long_format:
       for (i = 0; i < files_index; i++)
        {
-         print_long_format (files + i);
+         print_long_format (sorted_file[i]);
          DIRED_PUTCHAR ('\n');
        }
       break;
@@ -3980,9 +4004,10 @@ print_many_per_line (void)
       /* Print the next row.  */
       while (1)
        {
-         size_t name_length = length_of_file_name_and_frills (files + filesno);
+         struct fileinfo const *f = sorted_file[filesno];
+         size_t name_length = length_of_file_name_and_frills (f);
          size_t max_name_length = line_fmt->col_arr[col++];
-         print_file_name_and_frills (files + filesno);
+         print_file_name_and_frills (f);

          filesno += rows;
          if (filesno >= files_index)
@@ -4011,6 +4036,7 @@ print_horizontal (void)
   /* Now the rest.  */
   for (filesno = 1; filesno < files_index; ++filesno)
     {
+      struct fileinfo const *f;
       size_t col = filesno % cols;

       if (col == 0)
@@ -4024,9 +4050,10 @@ print_horizontal (void)
          pos += max_name_length;
        }

-      print_file_name_and_frills (files + filesno);
+      f = sorted_file[filesno];
+      print_file_name_and_frills (f);

-      name_length = length_of_file_name_and_frills (files + filesno);
+      name_length = length_of_file_name_and_frills (f);
       max_name_length = line_fmt->col_arr[col];
     }
   putchar ('\n');
@@ -4040,7 +4067,8 @@ print_with_commas (void)

   for (filesno = 0; filesno < files_index; filesno++)
     {
-      size_t len = length_of_file_name_and_frills (files + filesno);
+      struct fileinfo const *f = sorted_file[filesno];
+      size_t len = length_of_file_name_and_frills (f);

       if (filesno != 0)
        {
@@ -4061,7 +4089,7 @@ print_with_commas (void)
          putchar (separator);
        }

-      print_file_name_and_frills (files + filesno);
+      print_file_name_and_frills (f);
       pos += len;
     }
   putchar ('\n');
@@ -4199,7 +4227,8 @@ calculate_columns (bool by_columns)
   /* Compute the maximum number of possible columns.  */
   for (filesno = 0; filesno < files_index; ++filesno)
     {
-      size_t name_length = length_of_file_name_and_frills (files + filesno);
+      struct fileinfo const *f = sorted_file[filesno];
+      size_t name_length = length_of_file_name_and_frills (f);
       size_t i;

       for (i = 0; i < max_cols; ++i)
M ChangeLog
M bootstrap.conf
M src/ls.c
Committed as 5a9dbd9f46b0c2bc2bfc413281105fa19835a817