sorry in advance for this noob question.
can we repartition rootfs, optfs, etc i mean i noticed that when the rootfs got more memory the device is fast and when its full the device is slow. so y dont repartition? im sorry im new to linux plz answer. plz share your ideas.

I assume you're talking about the N900 (I am not familiar with the inner workings of the N9/N950 at all). From what I know/remember, and I might be off on some technical details:

rootfs is limited by the physical size of the chip on which it is stored.

Basically, the N900 has two flash storage places built in - a very small chip that, as I understand it, is built into the SoC ("System on a Chip", which is where they stick the CPU, RAM, and some storage on the same chip, common in embedded devices) - this is where the rootfs is stored, and rootfs partition already takes up that entire chip, and a separate 32 GB eMMC (which contains optfs and the "MyDocs" FAT partitions).

So you can't make rootfs bigger because it's as big as it can get already. You can however, manually move a bunch of stuff that really doesn't need to be in rootfs, into optfs. A lot of programs/apps already do this ;optifying', but a lot don't. For example, the build-in browser engine library and the majority of the Nokia Maps program don't really need to be in rootfs, but that's where Nokia put them. (I have a bunch of scripts lying around precisely for optifying a bunch of packages I always install, because once upon a time I had to reflash my N900 relatively frequently.)

You CAN repartition optfs. The easiest way (for me at least) is to do it when you're fully (complete except really special, stored-in-CAL settings like lock code) reflashing the N900, by hex-editing the actual eMMC image that Nokia provides. There's instructions on how to do it on the maemo.org wiki, I believe. Alternatively, if you don't want to reflash, you can do it using standard linux tools, the problem is, I personally don't know how. But the instructions for that are available on the wiki as well, most likely on the same page as the hex-editing+reflashing way.

but the eMMC also is flash right?

Yes. They are both flash storage, not the spinning disk hard drives. If I recall correctly, they are slightly different forms/types of flash storage, though. Not just at the file system used to format them level, but at the physical level.

Of course, because one (the rootfs chip) is so much physically closer and better integrated with the CPU (and possibly because of the physical difference in flash type), the access speeds to read/write data on rootfs are faster, than they are on the eMMC. But on the other hand, for most things (like running a program) the difference is not human-noticeable.

then i think i better close this thread cuz its useless to discuss