Re: [Qemu-devel] [PATCH] qga: add mountpoint usage to GuestFilesystemInfo

[Eric Blake]

On 05/30/2018 01:55 AM, Chen Hanxiao wrote:

> > > +    usage = u100 / nonroot_total + (u100 % nonroot_total != 0);
> >
> > Why integral instead of floating point?
>
> I followed the style of df from coreutils.
> As the percentage already multiplied by 100,
> I think it has enough precision.

You're making an arbitrary policy decision.  Give the client a floating 
point, and they can still truncate to print out a 2-digit percentage. 
But give them a percentage, and for a 2T disk image, they are forced to 
guess whether they are 20G high or low on usage, which starts to take a 
non-trivial amount of time to copy that much data.  In other words, I 
think an int is wrong for being too imprecise.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org