Memory issue when updating all entries from a channel (allowed memory size of X bytes exhausted (tried to allocate Y bytes))
If you just want to re-save a large number of entries without modifying them, you can run a ResaveElements task, which takes some basic parameters and re-saves all the entries that match them.

You can do that like this:

// Queue up a new ResaveElements task
craft()-&gt;tasks-&gt;createTask('ResaveElements', null, array(
    'elementType' =&gt; ElementType::Entry,
    'criteria'    =&gt; array('section' =&gt; 'mySectionHandle', 'limit' =&gt; null, 'status' =&gt; null, 'localeEnabled' =&gt; null)
));

// Start running tasks
craft()-&gt;tasks-&gt;runPendingTasks();