Xen Balloon Drivers For Mac

I hope you don't mind, but I cc-ed this back to the list. I figure that other folks might also be interested in a more detailed explanation since I was a little vague before! Thank you for your reply and I do not understand the meaning of 'The balloon driver just allocates loads of memory,',what does it mean? The way the balloon driver really works (at the moment) is to just allocate lots of memory. Once it's allocated by the balloon driver, it can't be used by anything else. The balloon driver can then safely return that memory to Xen, so the domain has been shrunk. The kernel thinks that the balloon driver has allocated loads of memory, whereas actually that memory is not there anymore.

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• Xen Balloon Driver For Mac

When you grow the domain again, the balloon driver retrieves memory from Xen, and then frees it back to the guest. From the kernel's point of view, the balloon driver has just released some memory it's been using.

and another one,' There have been some bad interactions with Linux's memory management code when using the balloon driver - particularly when using it aggressively to shrink a domain.' ,then could you give me a more detailed explaination about it? There have been cases in the past of the Linux memory management code getting upset by the balloon driver.

From the kernel's point of view if you shrink a domain from 256M to 32M it looks like some kind of serious memory crunch is happening, with too many things requesting allocations. This has been known to cause the Linux Out Of Memory (OOM) killer to come and destroy processes in order to free RAM - not good. This can happen if you shrink a domain so much that it doesn't have enough RAM for all its processes anymore. But it certainly used to happen even when there was enough RAM for the guest to keep operating, because the guest didn't understand what was happening. I believe this is been mitigated by modifications to the balloon driver which cause it to allocate memory more gradually when shrinking the domain, giving the guest a chance to cope. I don't know how much of a problem this is these days.

Anyhow, that's the basic idea of what's gone wrong in the past. To be honest, I'm not sure how much of a problem these things are now or whether there's anything else the roadmap had in mind to improve. It would certainly be cleaner if the ballooning operation could appear as a memory hotplug rather than just a lot of allocations; I don't know if that solves any of the memory crunch problems though (or how much of a problem these turn out to be nowadays). I do think that if you don't fancy hacking on the balloon driver mechanism itself, a daemon to automatically redistribute memory to the domains which need it (by using the balloon drivers) could be a cool project and potentially useful.

Cheers, Mark - Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels.

Mark: My wheel has a wheel! Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx.

I've been trying for months now. I saw it work twice (thanks, Bjorn!), but couldn't reproduce it myself, nor could the original user. One thing we definitely noticed is that networking can't be bridged, but rather must be host only.

What I see most of the time is that Xen boots, but the whole Parallels VM crashes when I try to run a guest within Xen. I keep reporting this when it occurs with new versions of Parallels, but obviously (for good reasons) this is way down their list of priorities. Still, if it runs on an x86, it 'should' run in Parallels. (resisting urge to snark) Emulators that use hardware support won't ever run under other emulators. Wait for the Mac version. Xen does have a mode that uses hardware support, but that support is quite new (VT), and it also runs on earlier hardware without that support. In that mode, I have seen Xen working, and in fact, with the latest version of Parallels (1922), last night I actually reproduced the successes I'd seen earlier.

I haven't narrowed down the settings that enabled this fully, but in addition to host-only networking, I believe that at least 1G needs to be assigned to Parallels for a DomU to boot. This is great news for me - because I want to do Xen hacking inside a virtual machine (as opposed to having to reboot my hardware when I cause kernel crashes). Log: Linux version 2.6.16.33-xen (root@localhost.localdomain) (gcc version 4.1.1 20061011 (Red Hat 4.1.1-30)) #3 SMP Mon Jan 15 17:34:37 CET 2007 BIOS-provided physical RAM map: Xen: 000000 - 800000 (usable) 0MB HIGHMEM available. 136MB LOWMEM available.

ACPI in unprivileged domain disabled Built 1 zonelists Kernel command line: root=/dev/sda1 ro Enabling fast FPU save and restore. Enabling unmasked SIMD FPU exception support. Initializing CPU#0 PID hash table entries: 1024 (order: 10, 16384 bytes) Xen reported: 1410.995 MHz processor. Console: colour dummy device 80x25 Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) Software IO TLB disabled vmalloc area: c9000000-fb7fe000, maxmem 33ffe000 Memory: 120088k/139264k available (1907k kernel code, 10828k reserved, 723k data, 188k init, 0k highmem) Checking if this processor honours the WP bit even in supervisor mode.

Calibratedelaydirect failed to get a good estimate for loopsperjiffy. Probably due to long platform interrupts. Consider using 'lpj=' boot option.

Security Framework v1.0.0 initialized Capability LSM initialized Mount-cache hash table entries: 512 CPU: L1 I cache: 32K, L1 D cache: 32K CPU: L3 cache: 4096K Checking 'hlt' instruction. Brought up 1 CPUs migrationcost=0 checking if image is initramfs. It is Freeing initrd memory: 4946k freed Grant table initialized NET: Registered protocol family 16 Brought up 1 CPUs PCI: setting up Xen PCI frontend stub ACPI: Subsystem revision 20060127 ACPI: Interpreter disabled. Linux Plug and Play Support v0.97 (c) Adam Belay pnp: PnP ACPI: disabled xenmem: Initialising balloon driver. PCI: System does not support PCI PCI: System does not support PCI IA-32 Microcode Update Driver: v1.14-xen audit: initializing netlink socket (disabled) audit(.190:1): initialized VFS: Disk quotas dquot6.5.1 Dquot-cache hash table entries: 1024 (order 0, 4096 bytes) Initializing Cryptographic API io scheduler noop registered io scheduler anticipatory registered io scheduler deadline registered io scheduler cfq registered (default) PNP: No PS/2 controller found. Probing ports directly. I8042.c: No controller found.

Floppy drive(s): fd0 is unknown type 15 (usb?), fd1 is unknown type 15 (usb?) Failed to obtain physical IRQ 6 floppy0: no floppy controllers found RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize loop: loaded (max 8 devices) Xen virtual console successfully installed as tty1 Event-channel device installed. Netfront: Initialising virtual ethernet driver. Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx mice: PS/2 mouse device common for all mice md: md driver 0.90.3 MAXMDDEVS=256, MDSBDISKS=27 md: bitmap version 4.39 NET: Registered protocol family 2 Registering block device major 8 blkfront: sda1: barriers enabled blkfront: sda2: barriers enabled -PARALLELS CRASHED.

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This is with RAMDISK disabled on Xen DomU config root@localhost # xm create -c fc3 Using config file '/etc/xen/fc3'. Started domain fc3 Linux version 2.6.16.33-xen (root@localhost.localdomain) (gcc version 4.1.1 20061011 (Red Hat 4.1.1-30)) #3 SMP Mon Jan 15 17:34:37 CET 2007 BIOS-provided physical RAM map: Xen: 000000 - 800000 (usable) 0MB HIGHMEM available.

136MB LOWMEM available. ACPI in unprivileged domain disabled Built 1 zonelists Kernel command line: root=/dev/sda1 ro Enabling fast FPU save and restore. Enabling unmasked SIMD FPU exception support. Initializing CPU#0 PID hash table entries: 1024 (order: 10, 16384 bytes) Xen reported: 1144.339 MHz processor. Console: colour dummy device 80x25 Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) Software IO TLB disabled vmalloc area: c9000000-fb7fe000, maxmem 33ffe000 Memory: 125052k/139264k available (1907k kernel code, 5880k reserved, 723k data, 188k init, 0k highmem) Checking if this processor honours the WP bit even in supervisor mode.

Calibrating delay using timer specific routine. 4905.47 BogoMIPS (lpj=24527384) Security Framework v1.0.0 initialized Capability LSM initialized Mount-cache hash table entries: 512 CPU: L1 I cache: 32K, L1 D cache: 32K CPU: L3 cache: 4096K Checking 'hlt' instruction.

Brought up 1 CPUs migrationcost=0 Grant table initialized NET: Registered protocol family 16 Brought up 1 CPUs PCI: setting up Xen PCI frontend stub ACPI: Subsystem revision 20060127 ACPI: Interpreter disabled. Linux Plug and Play Support v0.97 (c) Adam Belay pnp: PnP ACPI: disabled xenmem: Initialising balloon driver.

Xen Balloon Driver For Mac

PCI: System does not support PCI PCI: System does not support PCI IA-32 Microcode Update Driver: v1.14-xen audit: initializing netlink socket (disabled) audit(.795:1): initialized VFS: Disk quotas dquot6.5.1 Dquot-cache hash table entries: 1024 (order 0, 4096 bytes) Initializing Cryptographic API io scheduler noop registered io scheduler anticipatory registered io scheduler deadline registered io scheduler cfq registered (default) PNP: No PS/2 controller found. Probing ports directly. I8042.c: No controller found. Floppy drive(s): fd0 is unknown type 15 (usb?), fd1 is unknown type 15 (usb?) Failed to obtain physical IRQ 6 floppy0: no floppy controllers found RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize loop: loaded (max 8 devices) Xen virtual console successfully installed as tty1 Event-channel device installed. Netfront: Initialising virtual ethernet driver.