[libvirt][PATCH v4 0/3] introduce 'restrictive' mode in numatune

[Zhong, Luyao]

> -----Original Message-----
> From: Martin Kletzander <mkletzan at redhat.com>
> Sent: Thursday, March 25, 2021 4:46 AM
> To: Daniel P. Berrangé <berrange at redhat.com>
> Cc: Zhong, Luyao <luyao.zhong at intel.com>; libvir-list at redhat.com
> Subject: Re: [libvirt][PATCH v4 0/3] introduce 'restrictive' mode in numatune
> 
> On Tue, Mar 23, 2021 at 09:48:02AM +0000, Daniel P. Berrangé wrote:
> >On Tue, Mar 23, 2021 at 10:59:02AM +0800, Luyao Zhong wrote:
> >> Before this patch set, numatune only has three memory modes:
> >> static, interleave and prefered. These memory policies are ultimately
> >> set by mbind() system call.
> >>
> >> Memory policy could be 'hard coded' into the kernel, but none of
> >> above policies fit our requirment under this case. mbind() support
> >> default memory policy, but it requires a NULL nodemask. So obviously
> >> setting allowed memory nodes is cgroups' mission under this case.
> >> So we introduce a new option for mode in numatune named 'restrictive'.
> >>
> >> <numatune>
> >>    <memory mode="restrictive" nodeset="1-4,^3"/>
> >>    <memnode cellid="0" mode="restrictive" nodeset="1"/>
> >>    <memnode cellid="2" mode="restrictive" nodeset="2"/> </numatune>
> >
> >'restrictive' is rather a wierd name and doesn't really tell me what
> >the memory policy is going to be. As far as I can tell from the
> >patches, it seems this causes us to not set any memory alllocation
> >policy at all. IOW, we're using some undefined host default policy.
> >
> >Given this I think we should be calling it either "none" or "default"
> >
> 
> I was against "default" because having such option possible, but the actual
> default being different sounds stupid.  Similarly "none" sounds like no
> restrictions are applied or that it is the same as if nothing was specified.  It is
> funny to imagine the situation when I am explaining to someone how to achieve
> this solution:
> 
>    "The default is 'strict', you need to explicitly set it to 'default'."
> 
> or
> 
>    "What setting did you use?"
>    "None"
>    "As in no mode or in mode='none'?"
> 
> As I said before, please come up with any name, but not these that are IMHO
> actually more confusing.
> 

Hi Daniel and Martin, thanks for your reply, just as Martin said current default mode is "strict", so "default" was deprecated at the beginning when I proposed this change.  And actually we have cgroups restricting the memory resource so could we call this a "none" mode? I still don't have a better name. ☹

> >
> >Regards,
> >Daniel
> >--
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