I observed that everytime when emerging some things (not small ones: kdelibs, kdenetwork, firefox.. and so on), it keeps a lot of time after each install. Doing a ps -Af it tells me that it is deleting work directory which can lead to several minutes depending on number of files, file system, etc.. I propose to include a feature (maybe in FEATURES variable) to have that directory in a tmpfs mounted filesystem, and this way, the rm -rf (...)/work command can be skipped. This is also good for the sake of the life of laptop's hard drives (just an example) and could keep of wasting time several minutes in each emerge. As someone may think, maybe some programs could not compile due to lack of space, I think openoffice is one of them, in that case, it could be disabled by purpose.. Please, give me your opinion about this. Reproducible: Always
I don't thing we want to include this directly in portage but I've heard on something called bashrcng-shmfs that that's available in this overlay: http://gechi-overlay.sourceforge.net/
Not going to mount filesystems in portage (that's just going to cause trouble).
If you want to use this feature, you can set-up a tmpfs yourself and, in /etc/make.conf, point the PORTAGE_TMPDIR to it and add 'noclean' to FEATURES.