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[Xen-devel] RE: [PATCH][BALLOON] Fix minimum target

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH][BALLOON] Fix minimum target
From: "Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>
Date: Sat, 27 May 2006 16:34:07 -0400
Cc: Ky Srinivasan <KSrinivasan@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
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Thread-index: AcaBh+SdwaT1CL6pSGCKl/SacfB7CwAKMuSw
Thread-topic: [PATCH][BALLOON] Fix minimum target
> What happens if you set the min to 16MB + 2% of max-mem?

I changed the balloon driver to reflect this and found that DomU freezes
when it reaches around 2.2% - 3.1% of it initial allocation. I have the
data below for 2GB, 4GB, 8GB and 12GB DomUs. The MEM(k) below shows info
from xentop (with 1s delay) when the DomUs froze. Initial Alloc (%)is
what I calculated by hand. I am not sure how accurate xentop is so
Initial Alloc % could be a little lower than what is shown.

NAME        MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%) Initial Alloc(%)
2GBmem      66560    0.4    2101248      12.6   3.1 (xm mem-set id 32M)
4GBmem     113664    0.7    4198400      25.2   2.7 (xm mem-set id 64M)
8GBmem     205824    1.2    8392704      50.4   2.4 (xm mem-set id 64M)
12GBmem    281600    1.7   12587008      75.6   2.2 (xm mem-set id 64M)

So it looks like initial alloc % grows as domains get smaller. It does
not make sense. I think I am missing something here. Do you have any
clues? This could very well be the DomU crashing before xentop can
update the info.

I ran a few tests and it seems that setting the min to 64MB + 2% of
max-mem seems like a good option for DomUs.

Dom0 needs a much bigger floor of 192M. I think this is where KY came up
with the 192M number. I know this will cause problems on machines coming
up with dom0_mem<192M. 

Both these options will break xm-test. So how do you want to proceed?


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