A hack to /moodle/admin/settings/server.php
line 177 begins // performance settingpage
options in the pick list are hard coded beginning
One could add lines in the array.
'1536M' => '1536M',
'2048M' => '2048M'
make sure the line above the entry for 1536M ends with a ','
Values added will show in the pick list. Probably don't have to warn about hacks and updates, but just did. ;)
Another way ... add a line to config.php file:
$CFG->extramemorylimit = 'YOURVALUEM';
And for future reference, just about anything in mdl_conf table could be added to config.php. Might be better than the hack - easy to change.
'spirit of sharing', Ken