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Multi-wraps ----------- Previously, on every new timeout, we programmed registers LR=timeout and CMP=0. The counter than counted from LR down to 0, triggered the IRQ, jumped back to LR, and counted down again. If one installed small timeouts (< 1000 us), it was likely that the counter wrapped multiple times before we were able to read it out. Initially, this was not a big issue as the additional wraps were simply ignored and the amount of time lost through this was not big. But when we want to do correct rate limitation, multiple wraps cause an overflow in the additional calculations, and this has a big effect on the resulting time value. Thus, we now program the counter to start from ~0 and count down to 0. We set CMP=~0-timeout so that the timer still triggers the IRQ at the right time. The counter continues counting down after the IRQ has triggered until we install a new timeout. We do not consider anymore that the counter wraps. The maximum timeout is set to half the maximum counter value, so, we should be able to install a new timeout before the counter wraps. Rate limit for time updates --------------------------- In the time span between two interrupts we have to remember how many ticks we have already added to the time value. This is because at each call of curr_time we can only see how many ticks have passed since the last call of schedule_timeout and not since the last call of curr_time. But we want to limit the rate of time updates in curr_time. With the member for ticks that were already added since the last call to schedule_timeout we can then calculate how many are yet to be added.
=================================
Genode Operating System Framework
=================================
This is the source tree of the reference implementation of the Genode OS
architecture. For a general overview about the architecture, please refer to
the project's official website:
:Official project website for the Genode OS Framework:
[https://genode.org/documentation/general-overview]
The current implementation can be compiled for 8 different kernels: Linux,
L4ka::Pistachio, L4/Fiasco, OKL4, NOVA, Fiasco.OC, seL4, and a custom
kernel for running Genode directly on ARM-based hardware. Whereas the Linux
version serves us as development vehicle and enables us to rapidly develop the
generic parts of the system, the actual target platforms of the framework are
microkernels. There is no "perfect" microkernel - and neither should there be
one. If a microkernel pretended to be fit for all use cases, it wouldn't be
"micro". Hence, all microkernels differ in terms of their respective features,
complexity, and supported hardware architectures.
Genode allows the use of each of the kernels listed above with a rich set of
device drivers, protocol stacks, libraries, and applications in a uniform way.
For developers, the framework provides an easy way to target multiple different
kernels instead of tying the development to a particular kernel technology. For
kernel developers, Genode contributes advanced workloads, stress-testing their
kernel, and enabling a variety of application use cases that would not be
possible otherwise. For users and system integrators, it enables the choice of
the kernel that fits best with the requirements at hand for the particular
usage scenario.
Documentation
#############
The primary documentation is the book "Genode Foundations", which is available
on the front page of Genode website:
:Download the book "Genode Foundations":
[https://genode.org]
The book describes Genode in a holistic and comprehensive way. It equips you
with a thorough understanding of the architecture, assists developers with the
explanation of the development environment and system configuration, and
provides a look under the hood of the framework. Furthermore, it contains the
specification of the framework's programming interface.
The project has a quarterly release cycle. Each version is accompanied with
detailed release documentation, which is available at the documentation
section of the project website:
:Release documentation:
[https://genode.org/documentation/release-notes/]
Directory overview
##################
The source tree is composed of the following subdirectories:
:'doc':
This directory contains general documentation. Please consider the following
document for a quick guide to get started with the framework:
! doc/getting_started.txt
If you are curious about the ready-to-use components that come with the
framework, please review the components overview:
! doc/components.txt
:'repos':
This directory contains the so-called source-code repositories of Genode.
Please refer to the README file in the 'repos' directory to learn more
about the roles of the individual repositories.
:'tool':
Source-code management tools and scripts. Please refer to the README file
contained in the directory.
:'depot' and 'public':
Local depot and public archive of Genode packages. Please refer to
! doc/depot.txt
for more details.
Additional community-maintained components
##########################################
The components found within the main source tree are complemented by a growing
library of additional software, which can be seamlessly integrated into Genode
system scenarios.
:Genode-world repository:
[https://github.com/genodelabs/genode-world]
Contact
#######
The best way to get in touch with Genode developers and users is the project's
mailing list. Please feel welcome to join in!
:Genode Mailing Lists:
[https://genode.org/community/mailing-lists]
Commercial support
##################
The driving force behind the Genode OS Framework is the German company Genode
Labs. The company offers commercial licensing, trainings, support, and
contracted development work:
:Genode Labs website:
[https://www.genode-labs.com]