[Users] setting memory allocation

[Andrew Cranson (Layershift Limited)]

On x86 and x86-64 systems pages are measured in 4k - OVZ uses this these pages 
for resource allocation.

I believe you can also use M and G suffixes on recent OVZ package releases to 
set privvmpages/oomguarpages/vmguarpages. For example, "vzctl set $veid 
--vmguarpages 512M:600M" will translate to 131072:153600 (barrier:limit) pages 
automatically so you don't need to do to the math.

Regards,

Andrew Cranson
Layershift Limited
www.layershift.com

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Markus Hardiyanto wrote:
>   # RAM is 4k pages, so 131072*4k = 512M
>    vzctl set 1 --save --vmguarpages  131072
>    vzctl set 1 --save --oomguarpages 131072
>    vzctl set 1 --save --privvmpages  131072:196608
> 
> i thought all the numbers in beancounters was in bytes.. so why you divided it with 4k? 
> Best Regards,
> Markus
> 
> ----- Original Message ----
> From: Gregor Mosheh <gregor at hostgis.com>
> To: users at openvz.org
> Sent: Wednesday, May 2, 2007 9:46:52 PM
> Subject: Re: [Users] setting memory allocation
> 
> I'd like to take a shot at answering this, to "quiz myself" on how well I
> understand this stuff. So if my answers are incorrect or incomplete,
> please speak up!
> 
>> I have a computer with P4 2,4Ghz processor and 1GB of RAM. I'm planning to
>> split it into 3 VEs with this memory allocation:
>> VE1: 512MB
>> VE2: 256MB
>> VE3: 256MB
> 
> If by "memory allocation" you mean "the amount of RAM they're guaranteed
> to have available for use by apps" then try this:
> 
>    # RAM is 4k pages, so 131072*4k = 512M
>    vzctl set 1 --save --vmguarpages  131072
>    vzctl set 1 --save --oomguarpages 131072
>    vzctl set 1 --save --privvmpages  131072:196608
> 
> But, if you really have only 1 GB of RAM, it may not be wise to allocate
> all of it. If all of the VEs really use all their RAM, the system will
> start swapping to make up more RAM (e.g. for the HN's own use) and nobody
> enjoys a system that's swapping.
> 
> -Gregor
> 
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