Re: [PATCH v3] fallocate: Add "--dig-holes" option

[Karel Zak <kzak@redhat.com>]

On Mon, Feb 17, 2014 at 02:15:29PM +0000, Rodrigo Campos wrote:
> On Mon, Feb 17, 2014 at 11:32:48AM +0100, Karel Zak wrote:
> > On Fri, Feb 14, 2014 at 11:47:56AM +0100, Karel Zak wrote:
> > > On Sun, Jan 26, 2014 at 03:06:50PM +0000, Rodrigo Campos wrote:
> > > >  bash-completion/fallocate |   2 +-
> > > >  sys-utils/fallocate.1     |  19 +++++++-
> > > >  sys-utils/fallocate.c     | 114 ++++++++++++++++++++++++++++++++++++++++------
> > > >  3 files changed, 120 insertions(+), 15 deletions(-)
> > > 
> > >  Applied with some changes and I believe that the code still need some
> > >  improvements, see below
> > 
> > 
> >  OK, I did some changes to the code:
> > 
> >  The minimal hole size is based on filesystem blocksize (st_blksize) and 
> >  --length is no more used for this thing. I think it's better to use
> 
> This was not updated in the manpage, where it shows the run modes. It still
> says on the top "fallocate -d [-l length] filename"

 Oh.. synopsis. Thanks, fixed now.

> > 28K -rw-rw-r-- 1 kzak kzak 1.0G Feb 17 11:10 yyy
> > ^^^
> 
> How did you create the file ? With fallocate ? Is it all zeros ? If it's all
> zeros, 28K used seems like a bug maybe ?

 It's file with 6 holes with different sizes (1024, 10240, 102400 ....etc).

> Any comparisson to see how much it took before (to see the improvement or the

old version:

        $ ls -lash yyy
        1.1G -rw-rw-r-- 1 kzak kzak 1.0G Feb 17 15:39 yyy

        $ time ./fallocate --dig-holes
        yyy

        real    0m0.525s
        user    0m0.057s
        sys     0m0.463s

        $ ls -lash yyy
        164K -rw-rw-r-- 1 kzak kzak 1.0G Feb 17 15:39 yyy

 The 164K is because the small holes are ignored due to 32K buffer size.

 The speed improvement is probably because new code calls fallocate()
 only when end of the hole is detected. The another possibility is
 posix_fadvise(), but I have doubts that kernel readahead is so good.

> I can't test it in my new laptop because it fails to compile (autogen and
> configure run fine). It throws:
> 
> 	rm -f ca.gmo && : -c --statistics --verbose -o ca.gmo ca.po
> 	mv: cannot stat ‘t-ca.gmo’: No such file or directory
> 	make[3]: *** [ca.gmo] Error 1
> 
> 
> is this a known issue ?

 hmm... try git clean -xdf; ./autogen.sh ....

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com