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[Xen-users] Kernel memory initialisation

To: 'Xen List' <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] Kernel memory initialisation
From: "Olivier B." <xen.list@xxxxxxxxx>
Date: Mon, 18 Jul 2011 13:39:32 +0200
Delivery-date: Mon, 18 Jul 2011 04:40:53 -0700
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I have a small problem on small (128Mo) PV DomU : the kernel use too much memory.

By default if I start my DomU kernel ( with "memory = 128" in the xmdomain cfg, I obtain only 54MB of usable memory :

# head -n 1 /proc/meminfo
MemTotal:          54844 kB

While searching, I found that Xen (I guess) annouce 4GB of ram to the kernel, so in logs I have :

# grep Memory /var/log/kern.log | tail -n1
Jul 18 12:40:10 roy kernel: [ 0.000000] Memory: 46492k/4202496k available (2894k kernel code, 4063680k absent, 92324k reserved, 1826k data, 444k init)

Then I add mem=128M in "extra" area of my xmdomain cfg, and now I have a descent amount of usable memory (119MB) :

# head -n 1 /proc/meminfo
MemTotal:         122708 kB

# grep Memory /var/log/kern.log | tail -n1
Jul 18 13:14:10 roy kernel: [ 0.000000] Memory: 114356k/131072k available (2894k kernel code, 448k absent, 16268k reserved, 1826k data, 444k init)

But adding this parameter is not a "good" solution for me, so : is there a way to adjust the ratio of memory between the current memory usage and the amount of memory announced to the kernel ? (I only use 64bits systems)


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