As Confluence grow in size (eg. a few thousand of global spaces), inserting a link when editing a page will become slow (up to 10 seconds).

This is because the pull down menu includes a listing of all the available global spaces.

Confluence site search (ie. dosearchsite.action) will also be affected as the spaces are listed the same way as when inserting a link.

A work around is to comment out the control block in <confluence-install folder>/includes/common-space-select-box.vm and comment out the code section that calls for Global spaces to be listed:

#*
    #if ($availableSpaces.size() > 0)
    <optgroup label="$action.getText('global.spaces')">
        #foreach ($option in $availableSpaces)
            <option value="$option.key" #if( $searchQuery.spaceKey == $option.key ) selected#end>$webwork.htmlEncode($option.value)</option>
        #end
    </optgroup>
    #end
*#

Similarly to disable Global Space listing in confluence search, modify <confluence-install folder>/template/custom/space-select.vm:

#*
    #if ($availableGlobalSpaces.size() > 0)
    <optgroup label="$action.getText('global.spaces')">
        #foreach ($option in $availableGlobalSpaces)
            <option value="$option.key" #if( $value == $option.key ) selected#end>$webwork.htmlEncode($option.value)</option>
        #end
    </optgroup>
    #end
*#