Subject: Re: comparing raid-like filesystems
To: Chris Jepeway <>
From: Manuel Bouyer <>
List: tech-kern
Date: 02/02/2003 20:00:38
On Sun, Feb 02, 2003 at 01:31:51PM -0500, Chris Jepeway wrote:
> > Or allocate i[t] on stack, but I don't know of any way to
> > allocate a variable size on stack (I don't think alloca is allowed in
> > kernel). 
> I see what I think is a non-standard gcc extension at uvm_pager.c:294
> in uvm_aio_aiodone():
> 	struct vm_page *pg, *pgs[npages];
> This, from rev 1.59 of uvm_pager.c.  It crops up in uvm_bio.c v1.26, too.
> Is this usage...acceptable?  If so, well, there you go: variable-sized arrays.

I guess npages has to be computed before the array is declared ?
I'll have to look, but this may not be possible in the context.
However using alloca would work, and is probably as efficient as
variable-sized arrays.

Manuel Bouyer <>
     NetBSD: 24 ans d'experience feront toujours la difference