field_modules_enabled() greatly slows down profile installs, especially with features modules included

field_modules_enabled($modules) was added to field.module in 7.14, and really does a number on the speed of an install profile - the result is something like a 2x to 5x slowdown during the module installation batch calls depending on whether or not you are heavily using features modules (e.g. lots of content types and fields being defined).

/**
 * Implements hook_modules_enabled().
 */
function field_modules_enabled($modules) {
  // Refresh the 'active' status of fields.
  field_sync_field_status();
}

This is a big deal for groups like us, who have large install profiles.

From running profiling on the install, this slowdown appears to be just a very large number of operations (repeated module_invoke calls all the way down...) resulting from the field_sync_field_status() call - no one cause leaps out.

If you do this:

/**
 * Implements hook_modules_enabled().
 */
function field_modules_enabled($modules) {
  // Refresh the 'active' status of fields, but only after an install is
  // completed.
  if (variable_get('install_task') == 'done') {
    field_sync_field_status();
  }
}

You end up with speed restored to the 7.12 level, but you you don't get a proper installation - fields are not correctly attached to entities. So further investigation needed here to figure out why this is so much slower than the way it used to work.