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Re: [libvirt] [PATCH] Update docs for memory parameters and memtune command



On Mon, 18 Oct 2010 09:55:46 +0200, Matthias Bolte <matthias bolte googlemail com> wrote:
> 2010/10/18 Nikunj A. Dadhania <nikunj linux vnet ibm com>:
> > From: Nikunj A. Dadhania <nikunj linux vnet ibm com>
> >
> > docs/formatdomain.html.in: Add memtune element details
[...]
> > @@ -211,6 +216,22 @@
> >         <code>hugepages</code> element set within it. This tells the
> >         hypervisor that the guest should have its memory allocated using
> >         hugepages instead of the normal native page size.</dd>
> > +      <dt><code>memtune</code></dt>
> > +      <dd> The optional <code>memtune</code> element provides details
> > +      regarding the memory tuneable parameters for the domain. If this is
> > +      omitted, it defaults to the OS provided defaults.</dd>
> > +      <dt><code>hard_limit</code></dt>
> > +      <dd> The optional <code>hard_limit</code> element is the maximum memory
> > +       the guest can use. The units for this value are kilobytes (i.e. blocks
> > +       of 1024 bytes)</dd>
> 
> Well, the maximum of memory a guest can use is also controlled by the
> memory and currentMemory element in some way. How does hard_limit
> relate to those two?
>
memory and currentMemory are related to balloon size, while these are operating
system provided limits.
 
> > +      <dt><code>soft_limit</code></dt>
> > +      <dd> The optional <code>soft_limit</code> element is the memory limit to
> > +       enforce during memory contention. The units for this value are
> > +       kilobytes (i.e. blocks of 1024 bytes)</dd>
> 
> Is this an upper or a lower limit? Does it mean in case of contention
> this guest may only use up to soft_limit kilobytes of memory (upper
> limit)? Or does it mean in case of contention make sure that this
> guest can access at least soft_limit kilobytes of memory (lower
> limit)?
> 
Upper limit of memory the guest can use(i.e upto soft_limit) during
contention. Balbir, correct me if this isn't correct.

> How does this relate to the memory and currentMemory element?  
>
At present no relation, they are implemented by the OS.

> How does it related to the min_guarantee element?
> 
It is not related to min_guarantee.

> > +      <dt><code>swap_hard_limit</code></dt>
> > +      <dd> The optional <code>swap_hard_limit</code> element is the maximum
> > +       swap the guest can use. The units for this value are kilobytes
> > +       (i.e. blocks of 1024 bytes)</dd>
> 
> What about the min_guarantee element anyway? It's not implemented in virsh.
> 
Missed it, I will add the docs about min_gaurantee and send the updated
patch. It is not implemented in virsh. However, I have taken care of parsing
them in domain configuration.

Nikunj


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