[libvirt] Re: [PATCH] also allow use of XZ for Qemu image compression

[Charles Duffy]

Jim Meyering wrote:
> Good point about it being one of the fastest.
> I shouldn't have mentioned the subjective "popular".
> Usefulness trumps that.  I suppose Daniel, Cc'd, will decide.

Per off-list discussion with DV, I'm providing some numbers. Sort order 
is space used on disk, lowest to highest, with a 251MB file created by 
virDomainSave.

		comptime[*]	decomptime[*]	space
xz[default]	3m45.890s	4.960s		42MB
xz[0]		0m17.450s	6.080s		54MB
bzip2		0m56.290s	11.080s		58MB
gzip		0m13.790s	2.260s		64MB
lzop		0m1.970s	0.800s		87MB

I believe this makes the distinct niche of each of the compressors 
clear, with the exclusion of bzip2 (which is both slower and produces 
larger output compared to xz -0).


[*] "time" is user-mode CPU time, as reported by the bash "time" builtin 
on an Intel Xeon E7330 @ 2.40GHz.