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Re: [Libvir] [PATCH] Block device and network stats



On Mon, Aug 13, 2007 at 12:45:39PM +0100, Daniel P. Berrange wrote:
> On Mon, Aug 13, 2007 at 05:45:27AM -0400, Daniel Veillard wrote:
> > On Fri, Aug 10, 2007 at 03:35:08PM +0100, Richard W.M. Jones wrote:
> > > This is the implementation (currently Xen, local only).
> > 
> >   Thanks !
> > 
> > > +++ include/libvirt/libvirt.h.in	10 Aug 2007 14:30:21 -0000
> > > @@ -14,6 +14,9 @@
> > >  #ifndef __VIR_VIRLIB_H__
> > >  #define __VIR_VIRLIB_H__
> > >  
> > > +#include <sys/types.h>
> > > +#include <stdint.h>
> > > +
> > [...]
> > > +struct _virDomainBlockStats {
> > > +  int64_t rd_req;
> > 
> >   That's my only worry at the moment. stdint.h isn't really that portable,
> > we want to define an 64bits unsigned field, but we already use 
> >    unsigned long long 
> > in libvirt.h . I would be tempted to rationalize this, either we think
> > (stdint.h/int64_t) is more portable or long long is the one, but I would
> > prefer if we picked one and stick with it at the API level.
> 
> I don't mind one way or the other - there's not really much to choose 
> between them - int64_t is POSIX, while long long is C99. So both are 
> 'standards'. They've both been available on Linux & Solaris for as long
> as I can remember.
> 
> # info gcc
> "5.8 Double-Word Integers
> ========================
> 
> ISO C99 supports data types for integers that are at least 64 bits wide,
> and as an extension GCC supports them in C89 mode and in C++.  Simply
> write `long long int' for a signed integer, or `unsigned long long int'
> for an unsigned integer. "
> 
> 
> # info inttypes.h
> "If an implementation provides integer types with width 64 that meet these
>  requirements, then the following types are required: int64_t uint64_t"
> 
> 
> Rock, paper, scissors. C99 wins!

  The only difference is that in some future (hopefully we will be retired
by then ;-) long long may actually end up being say 128bits on some hardware.
Honnestly I don't care, since we are already using unsigned long long in the
header then let's stick to it and use it for the statistics too.

Daniel

-- 
Red Hat Virtualization group http://redhat.com/virtualization/
Daniel Veillard      | virtualization library  http://libvirt.org/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine  http://rpmfind.net/


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