Re: Raid0 needs more memory.

Alan Cox (alan@lxorguk.ukuu.org.uk)
Wed, 2 Jul 1997 08:09:40 +0100 (BST)

> As someone else has already suggested to me, I suppose I should have just
> fixed raid0 with vmalloc instead of "fixing" kmalloc. Probably would have
> been easier. What penalties are there for using vmalloc over kmalloc, if
> any?

vmalloc memory is logically but not physically contiguous and on a lot
of platforms it is also slightly slower to access sometimes (its not in the
single kernel 4Mb TLB on intel for example). The performance issue is
miniscule, the virtual nature of its mapping means its no use for DMAing
into.

Oh and finally you cannot vmalloc in an interrupt or bh

Alan