N (the number of times the timer interrupt is fired in each second, aka 'HZ') is a hard coded compile-time architecture-dependent constant. This is how true multitasking is implemented in all the general-purpose operating systems and is also what stops processes from being able to monopolize the CPU time: the timer interrupt will be fired regardless of what the process is doing and the operating system will be able to stop it (pre-emption). The scheduler then decides which process should run next - either the process that was running before the timer interrupt was fired or another process. Firing this interrupt causes a call to the operating system's process scheduler routines. To know what dyntick does, first you should know some basics: Traditionally, multitasking is implemented using a timer interrupt that is configured to fire N times in a second. This also allows to implement true high-resolution timers.ĭynticks (aka: dynamic ticks) is a configurable feature for x86 32bits (x86-64 and ARM support is already done but not ready for this release PPC and MIPS support are in the works) that changes the heart of the mechanism that allows a system to implement multitasking.
#Postview vmi edu Patch
The clockevents patch unifies the clock device handling so the kernel can use the timer capabilities of those devices in a unified manner.
#Postview vmi edu code
Previously, the handling of such devices was made in architecture-specific code preventing a unified method of using those devices. An example of a clock device is the device which makes timer interrupts. If you have problems with 2.6.21, please report it)Ĭlockevents is a building block of dynticks. (This feature touches a lot of low-level x86 code, so regressions are possible. Recommended LWN article: "Clockevents and dyntick" CPU hotplug support - a useful feature for data centers, where you can add/remove CPUs according to the load.It's possible to migrate a guest from an Intel CPU to an AMD CPU Live migration (the guest continues running even while being migrated) support.Initial paravirtualization support, which has much faster performance This release (KVM-15) brings many new features: KVM does evolve at a very fast pace, due to its clean design. More details about VMI can be found in this LWN article: " The VMI virtualization interface " A VMI-enabled kernel can also boot on bare hardware and no hypervisor with no performance impact (commit 1 2, 3, 4, 5, 6, 7, 8) Any hypervisor can use VMI by providing a (GPLed) ROM the ROM describes how the low-level VMI kernel must use the hypervisor. Vmware will certainly use VMI Xen was going to use VMI but they may develop their own VMI-like interface. The goal of VMI is to become the common paravirtualization interface for hypervisors like Xen and Vmware. Paravirtualizated kernels need to be modified to run under a hypervisor. VMI is a virtualization feature built in top of the paravirt_ops paravirtualization implementation introduced in 2.6.20. Important things (AKA: ''the cool stuff'')
#Postview vmi edu drivers
Other features are: bigger kernel command-line, optional ZONE_DMA support for the PA SEMI PWRficient CPU, for a Cell-based "celleb" architecture from Toshiba, better PS3 support: support for NFS IPv6, IPv4 IPv6 IPSEC tunneling support, UFS2 write support, kprobes for PPC32, kexec and oprofile for ARM, public key encryption for ecryptfs, Fcrypt and Camilla cipher algorithms, NAT port randomization, audit lockdown mode, many new drivers and many other small improvements. 2.6.21 also gets a tickless idle loop mechanism called "Dynticks" ( ), a feature built in top of "clockevents" which unifies the timer handling and brings true high-resolution timers.
KVM does get initial paravirtualization along with live migration and host suspend/resume support ( ).
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