Xen is a native, or bare-metal, hypervisor that allows multiple distinct virtual machines (referred to as domains) to share a single physical machine. As the highest privilege process on the system, Xen is responsible for the distribution of processor and memory resources between guest domains on the host. PV-on-HVM driver fixes and improvements (xen balloon driver and PV spinlocks support for HVM guests). Xen-gntalloc driver for userspace grant allocation between Xen domains. Xen-gntdev support for HVM guests.
For a certain job I sometimes need more memory in a DomU (CentOS 5).The trigger for the start of the job are some conditions that I can only check within that DomU: The DomU is waiting for an upload. Once it is finished it needs to process the received data - best suited would be a ram-disk.
For this scenario I have set up the DomU with a memory setting of 1 GB min and 16 GB max.
Now I am trying to find an elegant way to resize the memory to max/min from within the DomU.
The first solution for this would be using ssh from DomU to all possible Dom0s and then trigger the 'xm mem-set' commands there (with sudo).
I've read some things about the xen-store. Triggers were mentioned... So this makes me think that there should be a better way. It turned out that memory balloning would be a better way.
This should work within the DomU:
Should resize the memory to 4 GB.
But: cat /proc/xen/ballon says:
Now where does that xen hard limit come from?
Result is now that my DomU has 2 GB RAM.xm list in Dom0 states that the DomU is still at 1 GB RAM...
What's going wrong here?And yes - since the DomU-version is below 3.0.4 I added 'mem=16G' as kernel-boot-parameter to my DomU.
With Dom0 SLES11 SP1 (XEN 4.0.1) and CentOS 5.6 DomU (still XEN 3.0.3?) the echo 4G >/proc/xen/ballon did not do anything first - but after I did some successful xm mem-sets from the Dom0 (up to 16 GB - which worked), the /proc/xen/ballon did work within the DomU, too.
1 Answer
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you can use the balloon driver that xen has with min memory and max memory ... it's all dynamic and built in
silviudsilviud
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