dom0-min-mem parameter in xend-config.sxp

I guess no one ever responded to this?

The dom0-min-mem setting only controls
automatically-triggered ballooning (such as when creating a
VM.)  Explicit requests, like your "xm mem-set"
example, aren't limited by this setting.

We're assuming the admin knows what he's doing, but it
sounds like you want some extra vendor-specified limits to
keep things in a supportable configuration?  If we wanted to
do such a thing, I suppose the dom0-min-mem setting could
always be checked; if the admin really wanted to over-ride
this (at his own peril) he could edit the config file before
doing a lower mem-set.

Any comments for or against this approach?


>>> On Wed, Nov 15, 2006 at  9:00 AM, in message
<EF8D308BE33AF54D8934DF26520252D30350458CUSTR-EXCH5.na.uis.unisys.com>,
"Krysan, Susan" <KRYSANSunisys.com> wrote: 
> We boot our 128gb ES7000/one with dom0_mem=512M because
without it, it
> takes a while for dom0 to balloon down from 128gb when
creating larger
> domUs.  I would like to prevent users from ballooning
dom0 down any
> lower than 512, so I have set the value of dom0- min-
mem to 512 and
> rebooted.  When I do xm mem- set 0 256, the system
starts to balloon down
> (as seen using xm top) and then it freezes and becomes
unusable,
> requiring a reboot.  Shouldn't the dom0- min- mem value
prevent dom0 from
> attempting to balloon down to 256 when xm command is
used?  Or does it
> only control the minimum value for dom0 when the kernel
determines it
> needs to balloon?
> 
>  
> 
> Thanks,
> 
> Sue Krysan
> 
> Linux Systems Group
> 
> Unisys Corporation
> 
>  
> 
>  


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Charles,

There was a patch in the SLES10 Xen which imposed a hard
lower limit
(196Mb + 5%) on ballooning. I remember Ky Srinivasan saying
that this
would be in the SLES10 Xen even though it is not part of
unstable. 

Sue, please correct if I am wrong... I think with the gold
master we did
not see this issue. But after applying the first set of SUSE
updates we
started to see the hang. So was this hard limit removed?

> We're assuming the admin knows what he's doing, but it
sounds like you
> want some extra vendor-specified limits to keep things
in a
supportable
> configuration?  If we wanted to do such a thing, I
suppose the
dom0-min-
> mem setting could always be checked; if the admin
really wanted to
over-
> ride this (at his own peril) he could edit the config
file before
doing a
> lower mem-set.
> 
> Any comments for or against this approach?

I submitted such a patch but it was not accepted.
http://www.nabble.com/-PATCH--Make-%22xm
-mem-set%22-be-lower-bound-on-do
mX-min-mem-tf1608742.html#a4513746

Aravindh
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No, I've done some further testing and applying the Xen
security update
did not affect the problem.  Instead, it appears to be
related to high
host memory (128GB).  I opened bug 225481 for this problem. 


Thanks,
Sue Krysan
Linux Systems Group
Unisys Corporation
 
-----Original Message-----
From: Puthiyaparambil, Aravindh 
Sent: Friday, December 01, 2006 5:31 PM
To: Charles Coffing; xenpreview-devforge.novell.com; Krysan,
Susan
Cc: Subrahmanian, Raj; McAfee, Tommie M; Vessey, Bruce A;
Carb, Brian A
Subject: RE: [xenpreview-dev] dom0-min-mem parameter in
xend-config.sxp

Charles,

There was a patch in the SLES10 Xen which imposed a hard
lower limit
(196Mb + 5%) on ballooning. I remember Ky Srinivasan saying
that this
would be in the SLES10 Xen even though it is not part of
unstable. 

Sue, please correct if I am wrong... I think with the gold
master we did
not see this issue. But after applying the first set of SUSE
updates we
started to see the hang. So was this hard limit removed?

> We're assuming the admin knows what he's doing, but it
sounds like you
> want some extra vendor-specified limits to keep things
in a
supportable
> configuration?  If we wanted to do such a thing, I
suppose the
dom0-min-
> mem setting could always be checked; if the admin
really wanted to
over-
> ride this (at his own peril) he could edit the config
file before
doing a
> lower mem-set.
> 
> Any comments for or against this approach?

I submitted such a patch but it was not accepted.
http://www.nabble.com/-PATCH--Make-%22xm
-mem-set%22-be-lower-bound-on-do
mX-min-mem-tf1608742.html#a4513746

Aravindh
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