posix_fallocate(2)

[Alan Cox]

On Thu, Apr 14, 2011 at 2:35 PM, <mdf at freebsd.org> wrote:

> For work we need a functionality in our filesystem that is pretty much
> like posix_fallocate(2), so we're using the name and I've added a
> default VOP_ALLOCATE definition that does the right, but dumb, thing.
>
> The most recent mention of this function in FreeBSD was another thread
> lamenting it's failure to exist:
> http://lists.freebsd.org/pipermail/freebsd-ports/2010-February/059268.html
>
> The attached files are the core of the kernel implementation of the
> syscall and a default VOP for any filesystem not supporting
> VOP_ALLOCATE, which allows the syscall to work as expected but in a
> non-performant manner.  I didn't see this syscall in NetBSD or
> OpenBSD, so I plan to add it to the end of our syscall table.
>
> What I wanted to check with -arch about was:
>
> 1) is there still a desire for this syscall?
>

Page 10 of my paper at
http://www.jeffshafer.com/publications/papers/shafer_ispass10.pdf describes
how it could improve Hadoop performance (if properly implemented).  So, I
would encourage you to add it.

Alan