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viomb(4) [netbsd man page]

VIOMB(4)						   BSD Kernel Interfaces Manual 						  VIOMB(4)

viomb -- VirtIO memory ballooning driver SYNOPSIS
virtio* at pci? dev ? function ? viomb* at virtio? DESCRIPTION
virtio(4) defines an interface for efficient, standard, and extensible I/O between the hypervisor and the virtual machine. The viomb driver supports the virtio-compliant memory ballooning device. Memory ballooning works as follows: 1. The host operator requests a guest to return some amount of memory to the host (via e.g. Qemu monitor balloon command). 2. The hypervisor sends the request via VirtIO memory ballooning device. 3. The guest viomb driver requests allocation of that amount of physical memory from the NetBSD memory management system. 4. The viomb device tells the hypervisor the guest physical memory address of the allocated memory via VirtIO memory ballooning device. The sysctl node hw.viomb.npages shows the requested number of memory pages to return to the hypervisor, while hw.viomb.actual shows the actual number of memory pages that are already returned to the hypervisor. SEE ALSO
virtio(4), sysctl(8) Rusty Russell, IBM Corporation, Virtio PCI Card Specification, HISTORY
The viomb device driver appeared in NetBSD 6.0. BUGS
The userland interface should be same as the Xen ballooning device. BSD
November 26, 2011 BSD

Check Out this Related Man Page

VIRTIO_BLK(4)						   BSD Kernel Interfaces Manual 					     VIRTIO_BLK(4)

virtio_blk -- VirtIO Block driver SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file: device virtio_blk Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5): virtio_blk_load="YES" DESCRIPTION
The virtio_blk device driver provides support for VirtIO block devices. LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5). hw.vtblk.no_ident hw.vtblk.X.no_ident These tunables disable retrieving the device identification string from the hypervisor either globally or per-device. The default value is 0. hw.vtblk.writecache_mode hw.vtblk.X.writecache_mode These tunables determine the write cache mode globally or per-device. The mode can changed only if the ConfigWCE feature is negoti- ated. Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave it as-is. The default value is to leave as-is. SYSCTL VARIABLES
The following variables are available as sysctl(8) variables. dev.vtblk.X.writecache_mode The write cache mode of the device can be either writethrough (0) or writeback (1). If the ConfigWCE feature is negotiated, the write cache mode can be toggled between writethrough and writeback. SEE ALSO
virtio(4) HISTORY
The virtio_blk driver was written by Bryan Venteicher <>. It first appeared in FreeBSD 9.0. BSD
July 2, 2013 BSD
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