Re: [kvm-devel] [Qemu-devel] Re: [PATCH] Add support for a configuration file

[Laurent Vivier]

Le jeudi 15 mai 2008 à 15:04 +0300, Avi Kivity a écrit :
> Daniel P. Berrange wrote:
> > On Thu, May 15, 2008 at 11:04:47AM +0300, Avi Kivity wrote:
> >   
> >> Daniel P. Berrange wrote:
> >>     
> >>> With this kind of syntax, now tools generating config files need to make
> >>> up unique names for each drive. So you'll probably end up with them just
> >>> naming things based on the class name + a number appended.
> >>>  
> >>>       
> >> I would hope that tools don't have to resort to reading and writing 
> >> these config files.  Usually a management system would prefer storing 
> >> parameters in its own database, and writing a temporary config file just 
> >> to pass the data seems awkward.  I would much prefer to see the command 
> >> line and monitor retain full control over every configurable parameter.
> >>     
> >
> > I expect that libvirt will create config files - it is only a matter of
> > time before we hit the command line ARGV length limits - particularly
> > with the -net and -drive syntax. People already requesting that we support
> > guests with > 16 disks, and > 8 network cards so command lines get very
> > long. 
> >   
> 
> What are those limits, btw? ISTR 10240 words, but how many chars?

ARG_MAX - _SC_ARG_MAX
        The  maximum  length  of  the arguments to the exec(3) family of
        functions.  Must not be less than _POSIX_ARG_MAX (4096).

getconf ARG_MAX
131072

And from a configure log I have:

checking the maximum length of command line arguments: 98304

Regards,
Laurent
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