Re: Is there a "make hole" (truncate in middle) syscall?

Szakacsits Szabolcs
2003-12-05T23:27:04Z

On Fri, 5 Dec 2003, [iso-8859-1] M?ns Rullg?rd wrote:
> Szakacsits Szabolcs <szaka@sienet.hu> writes:
>
> >> What are the downsides of holes? [...] is there a performance penalty to
> >> having a file with 1000 4k holes in it, etc...)
> >
> > Depends what you do, what fs you use. Using XFS XFS_IOC_GETBMAPX you might
> > get a huge improvement, see e.g. some numbers,
> >
> > http://marc.theaimsgroup.com/?l=reiserfs&m=105827549109079&w=2
> >
> > The problem is, 0 general purpose (like cp, tar, cat, etc) util supports
> > it, you have to code your app accordingly.
>
> I found this paragraph in the man page of GNU cp:
>
> --sparse=WHEN

I meant using XFS_IOC_GETBMAPX. tar and cp sparse support is extremely
inefficient (Helge also misunderstood what I meant). Only XFS provides
support doing it the fastest way, without reading and analysing the data.

Szaka