169,293 research outputs found
GMEM: Generalized Memory Management for Peripheral Devices
This paper presents GMEM, generalized memory management, for peripheral
devices. GMEM provides OS support for centralized memory management of both CPU
and devices. GMEM provides a high-level interface that decouples MMU-specific
functions. Device drivers can thus attach themselves to a process's address
space and let the OS take charge of their memory management. This eliminates
the need for device drivers to "reinvent the wheel" and allows them to benefit
from general memory optimizations integrated by GMEM. Furthermore, GMEM
internally coordinates all attached devices within each virtual address space.
This drastically improves user-level programmability, since programmers can use
a single address space within their program, even when operating across the CPU
and multiple devices. A case study on device drivers demonstrates these
benefits. A GMEM-based IOMMU driver eliminates around seven hundred lines of
code and obtains 54% higher network receive throughput utilizing 32% less CPU
compared to the state-of-the-art. In addition, the GMEM-based driver of a
simulated GPU takes less than 70 lines of code, excluding its MMU functions.Comment: Finished before Weixi left Rice and submitted to ASPLOS'2
Braess paradox in a network with stochastic dynamics and fixed strategies
The Braess paradox can be observed in road networks used by selfish users. It
describes the counterintuitive situation in which adding a new, per se faster,
origin-destination connection to a road network results in increased travel
times for all network users. We study the network as originally proposed by
Braess but introduce microscopic particle dynamics based on the totally
asymmetric exclusion processes. In contrast to our previous work
[10.1103/PhysRevE.94.062312], where routes were chosen randomly according to
turning rates, here we study the case of drivers with fixed route choices. We
find that travel time reduction due to the new road only happens at really low
densities and Braess' paradox dominates the largest part of the phase diagram.
Furthermore, the domain wall phase observed in [10.1103/PhysRevE.94.062312]
vanishes. In the present model gridlock states are observed in a large part of
phase space. We conclude that the construcion of a new road can often be very
critical and should be considered carefully.Comment: 25 pages, 16 figure
Glider: A GPU Library Driver for Improved System Security
Legacy device drivers implement both device resource management and
isolation. This results in a large code base with a wide high-level interface
making the driver vulnerable to security attacks. This is particularly
problematic for increasingly popular accelerators like GPUs that have large,
complex drivers. We solve this problem with library drivers, a new driver
architecture. A library driver implements resource management as an untrusted
library in the application process address space, and implements isolation as a
kernel module that is smaller and has a narrower lower-level interface (i.e.,
closer to hardware) than a legacy driver. We articulate a set of device and
platform hardware properties that are required to retrofit a legacy driver into
a library driver. To demonstrate the feasibility and superiority of library
drivers, we present Glider, a library driver implementation for two GPUs of
popular brands, Radeon and Intel. Glider reduces the TCB size and attack
surface by about 35% and 84% respectively for a Radeon HD 6450 GPU and by about
38% and 90% respectively for an Intel Ivy Bridge GPU. Moreover, it incurs no
performance cost. Indeed, Glider outperforms a legacy driver for applications
requiring intensive interactions with the device driver, such as applications
using the OpenGL immediate mode API
Smart Sensing Systems for the Daily Drive
When driving, you might sometimes wonder, "Are there any disruptions on my regular route that might delay me, and will I be able to find a parking space when I arrive?" Two smartphone-based prototype systems can help answer these questions. The first is ParkSense, which can be used to sense on-street parking-space occupancy when coupled with electronic parking payment systems. The second system can sense and recognize a user's repeated car journeys, which can be used to provide personalized alerts to the user. Both systems aim to minimize the impact of sensing tasks on the device's lifetime so that the user can continue to use the device for its primary purpose. This department is part of a special issue on smart vehicle spaces
RFID-Based IoT Scanning System for Tracking Parking Slot Application
The increasing demand for parking spaces in various facilities, such as shopping centers, ports, and airports, poses a significant challenge for parking managers. Drivers waste time and fuel searching for available parking slots, resulting in increased air pollution and negative environmental and health impacts. Therefore, a new solution is needed to address these issues and improve parking management efficiency. A parking management system that utilizes RFID technology and allows for the RFID Tag on each car to display user data, user ID, and parking space reservations is needed to improve the efficiency and convenience of parking at various facilities. The proposed system design incorporates various components, including a Camera Sensor, Raspberry PI, ESP8266, UHF RFID reader, and RFID Tag. The RFID technology captures radio waves emitted by the RFID Tag, enabling individual identification through unique codes. Testing revealed high accuracy at close range but decreased effectiveness at longer distances. Internet speed and network latency affected system performance, with faster speeds enabling faster data transmission. The system, developed using Thunkable and Firebase, provides real-time parking space availability information and streamlines vehicle entry and exit processes through RFID technology. This system has the potential to greatly improve the parking experience at busy public facilities by facilitating efficient parking spot finding and enhancing overall convenience for drivers
Urban road user charging and workplace parking levies
In this chapter we will briefly describe the provision made for the introduction of road user charging and workplace parking levies in the Transport Act 2000 and equivalent legislation for London and Scotland. After reviewing the background to these provisions, we will discuss the practical issues and policy questions which arise for any local authority wishing to take advantage of their new powers. Our discussion will draw attention to developments that have occurred since the passing of the Act and conclude on the prospects for charging schemes in the UK
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