Re: [Xen-devel] [PATCH v3 3/3] xl: Improve xl documentation in regards to guest memory management

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Daniel Kiper writes ("[Xen-devel] [PATCH v3 3/3] xl: Improve xl documentation 
in regards to guest memory management"):
> Improve xl documentation in regards to guest memory management.

Thanks.

> +=item B<mem_set_enforce_limit=BOOLEAN>
> +
> +If enabled, then C<xl mem-set> by default will set a memory allocation
> +target and enforce the maximum memory allocation for a given domain.
> +If disabled, then C<xl mem-set> by default will set a memory allocation
> +target only for a given domain.

I think you mean "for each domain" rather than "for a given domain",
and "will set only a memory allocation target for each domain" ?

> +The memory allocation target is a suggested amount of memory which
> +should be allocated by a guest. It is nice when the guest follows this
> +value but it may have its own idea about memory requirments. However,
> +it could not allocate more memory than a ceiling known as the maximum
> +memory allocation.

I would write "However the guest is prevented by Xen from allocating
more memory than a ceiling known as the "xen maximum" memory
allocation" or some such.

> --- a/docs/misc/libxl_memory.txt
> +++ b/docs/misc/libxl_memory.txt
> @@ -15,14 +15,19 @@
>               |  |          |  |    |        | target  |          | 
>               |  | guest    |  |    | build  |         |          | 
>               |  |          |  |    | start  |         |          | 
> -      static |  |          |  |    |        |         |          | 
> -     maximum |  +----------+  |    +        +         +          + 
> -             |  |          |  | 
> -             |  |          |  | 
> +             |  |          |  |    |        |         |          | 
> +             |  +----------+  |    +        +         +          + 
> +      static |  |          |  | 
> +     maximum |  |          |  | 
>               |  | balloon  |  | build 
>               |  |          |  | maximum 
>               |  |          |  | 
> -             +  +----------+  + 
> +             |  +----------+  + 
> +             |  |          |
> +             |  | memory   |
> +             |  | hotplug  |
> +             |  |          |
> +             +  +----------+

This change to the diagram implies that the target, and and the xen
maximum, never include any hotplug memory.  I don't think that can be
true.

Presumably hotplugged memory can be ballooned too.  So perhaps we need
another column ?

>  #### ~/memory/target = MEMKB []
>  
>  The current balloon target for the domain. The balloon driver within
> -the guest is expected to make every effort to every effort use no more
> -than this amount of RAM.
> +the guest is expected to make every effort to use no more than this
> +amount of RAM.

Good fix.

It might be worth adding:

  "Guests whose actual allocation exceeds the target may experience
   memory allocation failures."

Thanks,
Ian.

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