Does modifying read cache on my SD card also affect the speed of reading my Ext3 partition?

I'm trying to make Link2SD work on my phone so I partitioned my 16gb SD to 4gb for the Ext3 partition and the rest for normal storage. I'm noticing some slight lag on my usage of the phone and I read on this article that I can in fact, increase the read cache to speed up reading contents on the SD. My question is; does increasing the read cache also affect the speed of reading my Ext3 partition? Or does it only affect the "normal" storage?