Slat

A slat is a long, thin, flat piece of material (typically lumber or plastic).

Slat or slats may also refer to:

Common meanings

Arts and entertainment

SLAT

People

Leading-edge slats

Slats are aerodynamic surfaces on the leading edge of the wings of fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are usually used while landing or performing maneuvers which take the aircraft close to the stall, but are usually retracted in normal flight to minimize drag.

Types

Types include:

Operation

The chord of the slat is typically only a few percent of the wing chord. The slats may extend over the outer third of the wing, or they may cover the entire leading edge. Many early aerodynamicists, including Ludwig Prandtl believed that slats work by inducing a high energy stream to the flow of the main airfoil thus re-energizing its boundary layer and delaying stall. In reality, the slat does not give the air in the slot high velocity (it actually reduces its velocity) and also it cannot be called high-energy air since all the air outside the actual boundary layers has the same total heat. The actual effects of the slat are:

Second Level Address Translation

Second Level Address Translation (SLAT), also known as nested paging, is a hardware-assisted virtualization technology which makes it possible to avoid the overhead associated with software-managed shadow page tables.

Intel's implementation of SLAT, known as Extended Page Table (EPT), was introduced in the Nehalem microarchitecture found in certain Core i7, Core i5, and Core i3 processors. AMD supports SLAT through the Rapid Virtualization Indexing (RVI) technology since the introduction of its third-generation Opteron processors (code name Barcelona).

ARM's virtualization extensions support SLAT, known as Stage-2 page-tables provided by a Stage-2 MMU. The guest uses the Stage-1 MMU. Support was added as optional in the ARMv7ve architecture and is also supported in the ARMv8 (32-bit and 64-bit) architectures.

Overview

Modern processors use the concepts of physical memory and virtual memory; running processes use virtual addresses and when an instruction requests access to memory, the processor translates the virtual address to a physical address using a page table or TLB. When running a virtual system, it has allocated virtual memory of the host system that serves as a physical memory for the guest system, and the same process of address translation goes on also within the guest system. This increases the cost of memory access since the address translation needs to be performed twice – once inside the guest system (using software-emulated shadow page table), and once inside the host system (using hardware page table).