Re: [Xen-devel] [RFC PATCH 1/3] xl: replace vcpu-set --ignore-host with --ignore-warn

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Jul 23, 2013 at 12:29:36AM +0100, George Dunlap wrote:
> On 07/19/2013 04:48 PM, Konrad Rzeszutek Wilk wrote:
> >When Xen 4.3 was released we had a discussion whether we should
> >allow the vcpu-set command to allow the user to set more than
> >physical CPUs for a guest. The author brought up:
> >  - Xend used to do it,
> >  - If a user wants to do it, let them do it,
> >  - The original author of the change did not realize the
> >    side-effect his patch caused this and had no intention of changing it.
> >  - The user can already boot a massively overcommitted guest by
> >    having a large 'vcpus=' value in the guest config and we allow
> >    that.
> >
> >Since we were close to the release we added --ignore-host parameter
> >as a mechanism for a user to still set more vCPUs that the physical
> >machine as a stop-gate.
> >
> >This patch removes said option and adds the --ignore-warn option.
> >By default the user is allowed to set as many vCPUs as they would like.
> >We will print out a warning if the value is higher than the physical
> >CPU count. The --ignore-warn will silence said warning.
> 
> I think this is a good change in general, but I don't think the name
> is quite right.  You're not ignoring the warnings, you're turning
> them off.  Maybe make the function argument "warn", and the option
> "--no-warn"?

--silence?

If we were to use the --no-warn any thoughts on the short
version of it ? '-n' is a bit odd. I like the '-s'..

> 
> >+    host_cpu = libxl_get_max_cpus(ctx);
> >+    if (max_vcpus > host_cpu && !ignore_warn) {
> >+        fprintf(stderr, "WARNING: You are overcommmitting! You have %d" \
> >+                " physical CPUs and want %d vCPUs! Continuing, use" \
> >+                " --ignore-warn to silence this.\n", host_cpu, max_vcpus);
> >      }
> 
> This is relatively minor, but you might as well keep the same basic
> structure here, and only call libxl_get_max_cpus() if warn is set.

<nods>
> 
>  -George
> 
> 
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