I think, there is some kind of memory leak if i enable kdeenablefinal. Kdelib and kdebase builds with no problem with this use flag, but emerging kmail, makes system do a lot of swapping. I have 1 Gb memory, so i think this should be enough. If i disable this use flag, when emerging kmail, there are no problems.
Kindly read the flag description... *** This bug has been marked as a duplicate of 114860 ***