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List: xen-users
Subject: Re: [Xen-users] very strange problem: memory memory?
From: "chengkunck () gmail ! com" <chengkunck () gmail ! com>
Date: 2014-11-17 12:04:59
Message-ID: 201411172004530584175 () gmail ! com
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Hi Lee,
I think that it maybe not the VM who remembers the memory configuration. First, \
I've never met this problem mostly because my domus run linux and I seldomly change \
their configs. Then, it did remind me something that for a physical machine the BIOS \
would monitor the hardware changes, especially when you have a Windows and plug or \
unplug a memory chip. So my guess is it might be with the hypervisor, if my memory \
is correct, I remember there's also a mechanism for VM that serves as the BIOS. \
'ROMBIOS', it seems to be that name.
Best regards,
Kenneth
From: Ian Campbell
Date: 2014-11-17 17:54
To: lee
CC: xen-users
Subject: Re: [Xen-users] very strange problem: memory memory?
On Sat, 2014-11-15 at 00:26 +0100, lee wrote:
> Hi,
>
> does xen, or do domUs, somehow remember how much memory they had
> assigned to them?
>
> I've upgraded the memory of the server from 8GB to 36GB (8x4 + 4*1 GB),
> following the instructions in the manual about how to populate the
> banks. So far, the server is running fine.
>
> I have a VM which used to have 'memory = 3107' in its configuration.
> When I change the number to 10240 or 8192 or 4096 or even 3110, the VM
> crashes early during the boot process. Change it back to 3107 and the
> VM runs fine.
>
> There are other domUs that crash when they are booting when I change the
> amount of memory assigned to them, like from 384MB to 512MB. Change it
> back to 384MB and the VM runs fine. Only for two or three VMs, I was
> able to increase the memory.
>
> Dom0 and all domUs are running Debian Wheezy.
>
>
> Any idea what's going on here? Am I doing something wrong?
>
> The only thing that comes to mind is that for some reason, there's a
> strange problem with RAM modules of different sizes. But if that's the
> case, why is the server (IBM x3650 l2g) running fine?
Have you run memtest or something similar? It may be that some memory is
not used until you start a VM, because it is just in the free pool.
Ian.
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http://lists.xen.org/xen-users
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charset=ISO-8859-1"><style>body { line-height: 1.5; }blockquote { margin-top: 0px; \
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<div><span></span>Hi Lee,</div><div><span style="font-family: "" segoe="" \
ui'";="" font-size:="" 14px;="" color:="" rgb(0,="" 0,="" 0);="" background-color:="" \
rgba(0,="" font-weight:="" normal;="" font-style:="" normal;text-decoration:="" \
none;'=""> I think that it maybe not the VM who remembers the memory \
configuration. First, I've never met this problem mostly because my domus run linux \
and I seldomly change their configs. Then, it did remind me something that for a \
physical machine the BIOS would monitor the hardware changes, especially when you \
have a Windows and plug or unplug a memory chip. </span></div><div><span \
style="font-family: "" segoe="" ui'";="" font-size:="" 14px;="" color:="" \
rgb(0,="" 0,="" 0);="" background-color:="" rgba(0,="" font-weight:="" normal;="" \
font-style:="" normal;text-decoration:="" none;'=""> So my guess is it \
might be with the hypervisor, if my memory is correct, I remember there's also a \
mechanism for VM that serves as the BIOS. '</span><span style="font-family: ''; \
font-size: 10.5pt; line-height: 1.5; background-color: window;">ROMBIOS</span><span \
style="font-family: ''; font-size: 10.5pt; line-height: 1.5; background-color: \
window;">', it seems to be that name.</span></div> <div><br></div><hr style="width: \
210px; height: 1px;" color="#b5c4df" size="1" align="left"> <div><span>Best \
regards,<div> Kenneth</div></span></div> <blockquote \
style="margin-top: 0px; margin-bottom: 0px; margin-left: \
0.5em;"><div> </div><div style="border:none;border-top:solid #B5C4DF \
1.0pt;padding:3.0pt 0cm 0cm 0cm"><div style="PADDING-RIGHT: 8px; PADDING-LEFT: 8px; \
FONT-SIZE: 12px;FONT-FAMILY:tahoma;COLOR:#000000; BACKGROUND: #efefef; \
PADDING-BOTTOM: 8px; PADDING-TOP: 8px"><div><b>From:</b> <a \
href="mailto:Ian.Campbell@citrix.com">Ian \
Campbell</a></div><div><b>Date:</b> 2014-11-17 17:54</div><div><b>To:</b> <a \
href="mailto:lee@yagibdah.de">lee</a></div><div><b>CC:</b> <a \
href="mailto:xen-users@lists.xen.org">xen-users</a></div><div><b>Subject:</b> Re: \
[Xen-users] very strange problem: memory memory?</div></div></div><div><div>On Sat, \
2014-11-15 at 00:26 +0100, lee wrote:</div> <div>> Hi,</div>
<div>> </div>
<div>> does xen, or do domUs, somehow remember how much memory they had</div>
<div>> assigned to them?</div>
<div>> </div>
<div>> I've upgraded the memory of the server from 8GB to 36GB (8x4 + 4*1 \
GB),</div> <div>> following the instructions in the manual about how to populate \
the</div> <div>> banks. So far, the server is running fine.</div>
<div>> </div>
<div>> I have a VM which used to have 'memory = 3107' in its configuration.</div>
<div>> When I change the number to 10240 or 8192 or 4096 or even 3110, the \
VM</div> <div>> crashes early during the boot process. Change it back to \
3107 and the</div> <div>> VM runs fine.</div>
<div>> </div>
<div>> There are other domUs that crash when they are booting when I change \
the</div> <div>> amount of memory assigned to them, like from 384MB to \
512MB. Change it</div> <div>> back to 384MB and the VM runs fine. Only \
for two or three VMs, I was</div> <div>> able to increase the memory.</div>
<div>> </div>
<div>> Dom0 and all domUs are running Debian Wheezy.</div>
<div>> </div>
<div>> </div>
<div>> Any idea what's going on here? Am I doing something wrong?</div>
<div>> </div>
<div>> The only thing that comes to mind is that for some reason, there's a</div>
<div>> strange problem with RAM modules of different sizes. But if that's \
the</div> <div>> case, why is the server (IBM x3650 l2g) running fine?</div>
<div> </div>
<div>Have you run memtest or something similar? It may be that some memory is</div>
<div>not used until you start a VM, because it is just in the free pool.</div>
<div> </div>
<div>Ian.</div>
<div> </div>
<div> </div>
<div>_______________________________________________</div>
<div>Xen-users mailing list</div>
<div>Xen-users@lists.xen.org</div>
<div>http://lists.xen.org/xen-users</div>
</div></blockquote>
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