Xen Balloon Driver

This option is also not required for toolstack-directed ballooning. In reply to this post by Chu Rui As George pointed out in a separate branch of this email thread, disabling a guests caching is probably a bad idea in general. An interesting enhancement would be to collect statistics from the domains about how much memory they require and modify their memory footprints accordingly. After allocating the page, it puts it on its list of xen balloon and finds the gpfn for that page. Eventually, the number of outstanding Xen balloon entries is equal to the number of entries in the PoD pool, and the system is now in a stable state.

Balloon driver and oom-killer

The xen balloon reason for having the the PoD pool is that xen balloon memory is already allocated to the domain. At that point, Xen ballopn have no choice but to kill the xen balloon.

In reply to this post by Daniel Kiper. New Bug report received and forwarded.

Re Balloon driver for Linux/HVM

To see why this is important, consider the following scenario. Every useable gpfn must have a mfn behind it. As a workaround I would suggest starting all guests with an initial allocation that corresponds to the maximum they may ever use. Thank you for your kind reply, George.

In my perspective, PoD mainly works in the system initialization stage. The key is that the state of a gpfn after it has been scrubbed by the operating system is the same as the default initial state of a gpfn just populated by the PoD code.

The balloon driver can then safely return that memory to Xen, so the domain has been shrunk. It can do this because it only needs to allow the guest to run until the balloon driver can start. There have been cases in the past of the Linux memory management code getting upset by the balloon driver. This implies that Windows would have to be modified to use tmem, canon color imagerunner c3080i driver though it has been suggested that a Windows kernel expert might be able to somehow interpose binary code to do a similar thing.

XEN BALLOON DRIVER DOWNLOAD

Yes, it is - memory hotplug. Since I know nothing about Windows, someone else will have to explore that. So PoD memory may work well in that case.

Re Balloon driver for Linux/HVM

Balloon driver and oom-killer

If so, could you tell me the method you are using? After allocating the page, it puts it on its list of pages and finds the gpfn for that page.

Ballooning rebooting and the feature you ve never heard of

Every useable gpfn xen balloon have xen balloon mfn behind it. While the balloon keeps work all of the time. Ballooning then works like this.

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The primary one is that when populating a new PoD entry, we look at recently populated entries and see if they are zero, and if they are, we reclaim them. At that point, Xen would have no choice but to kill the guest. As you may know, ballooning is a technique used to dynamically xen balloon the physical memory in use by a guest. Would you please tell me whether my thought is correct?

Now it is under development. Information forwarded to debian-bugs-dist lists. If I recall correctly, it records the amount of high and low memory that has been ballooned out at the current time. The effect of this is to have each scrubbing thread only have one outstanging PoD page at balloom time.

Re Balloon driver and oom-killer

However, it is a long way to some extent to fully working implementation containing all features ballooning, tmem and memory hotplug. Because this method is very slow, it is only used as a last resort.

Would you please tell me how slow it is? So it begins allocating pages from the guest operating system, and freeing the gpfns back to Xen.

This is where populate-on-demand comes in. As George pointed out in a separate branch of this email thread, disabling a guests caching is probably a bad idea in general. But one of the beauties of Open Source software is that modification of the software stack is always an option. Most operating systems will only check how much memory is available at boot time.

Unfortunately, the real world is often a bit more messy than we would like. Now, we need to add the new kernel to the grub menu.

After that, its job is done. How does populate on demand deal with that?

Ballooning rebooting and the feature you ve never heard of