Linked by nfeske on Thu 26th May 2011 11:41 UTC
The concern for efficient and easy-to-use inter-process communication is prevalent among microkernel-based operating systems. Genode has always taken an unorthodox stance on this subject by disregarding the time-tested standard solution of using an IDL compiler in favour of sticking to raw C++ mechanisms. The new version 11.05 of the OS framework takes another leap by introducing a brand new API for implementing procedure calls across process boundaries, facilitating type safety and ease of use, yet still not relying on external tools. Furthermore, the platform support for the Fiasco.OC kernel has been extended to the complete feature set of the framework. The most significant new features are L4Linux (on Fiasco.OC), an experimental integration of GDB, ARM RealView PBX device drivers, and device I/O support for the MicroBlaze platform.
Thread beginning with comment 474805
To view parent comment, click here.
To read all comments associated with this story, please click here.
To view parent comment, click here.
To read all comments associated with this story, please click here.
RE[2]: Best approach is shared memory buffers.
by axilmar on Fri 27th May 2011 16:31
in reply to "RE: Best approach is shared memory buffers."
Member since:2006-03-20
Isn't the semaphore also a kernel-provided mechanism, which forces both processes to synchronize via kernel entries?
It doesn't have to be a kernel object.
Also, the usage of a shared-memory communication comes not for free as one has to establish the shared memory with each communication partner
Not a problem. The virtual memory subsystem can take care of that.
allocate buffers in the shared memory
Can be done via mutexes (not kernel objects) in shared memory.
acknowledge completed messages for buffer reuse
The buffers are simply freed from the shared memory.
maybe unblock the sender that wants to marshal the next message
Atomically increment the semaphore. If the other CPU spins on the semaphore (i.e. it's a spin lock), then the other process will be unblocked.
Modern microkernels like Fiasco.OC support fast inter-process communication with a user-level accessible part of the thread control block - UTCB - with a size of about 64 register words or something more. Processes marshal their message payload into the UTCB, the kernel copies from sender to receiver UTCB, and, finally, the receiver demarshals the data out of the UTCB as needed. Performance-wise this should fit the approach you described, the time for the copy operation is bounded by UTCB size, and there's no shared-memory establishment overhead as only the kernel accesses both UTCBs.
The 80x86 CPU doesn't have 64 registers available for users. Furthermore, you still do two kernel switches. I think the shared memory approach is faster, at least on 80x86.
News
Linked by Thom Holwerda on 05/18/13 7:37 UTC
"In NixOS, the entire operating system - the kernel, applications, system packages, configuration files, and so on - is built by the Nix package manager from a description in a purely functional build language. The fact that it's purely functional essentially means that building a new configuration cannot overwrite previous configurations. Most of the other features follow from this." Interesting approach. A Linux distribution, sure, but with some very refreshing ideas about system configuration.
Linked by fran on 05/18/13 1:38 UTC
Google added, among other features, C/C++ support to its new version of AIDE. From Android-IDE, "Now you can write parts of your app or your whole app in C/C++ on your device. AIDE supports the Standard Android NDK toolchain (GCC 4.6 + Bionic, STL, ...). No changes are necessary if you want to build an app developed on a PC with Eclipse. C/C++ development is fully integrated: Build errors appear in the error list and files can easily be navigated to with Go to file. The editor supports C/C++ syntax highlighting."
Linked by Thom Holwerda on 05/17/13 23:35 UTC, submitted by kragil
Ars nails it: "The answer is that Google did announce what amounts to a fairly substantial Android update yesterday. They simply did it without adding to the update fragmentation problems that continue to plague the platform. By focusing on these changes and not the apparently-waiting-in-the-wings update to the core software, Google is showing us one of the ways in which it's trying to fix the update problem."
Linked by MOS6510 on 05/17/13 22:22 UTC
"It is good for programmers to understand what goes on inside a processor. The CPU is at the heart of our career. What goes on inside the CPU? How long does it take for one instruction to run? What does it mean when a new CPU has a 12-stage pipeline, or 18-stage pipeline, or even a 'deep' 31-stage pipeline? Programs generally treat the CPU as a black box. Instructions go into the box in order, instructions come out of the box in order, and some processing magic happens inside. As a programmer, it is useful to learn what happens inside the box. This is especially true if you will be working on tasks like program optimization. If you don't know what is going on inside the CPU, how can you optimize for it? This article is about what goes on inside the x86 processor's deep pipeline."
Linked by Thom Holwerda on 05/17/13 22:15 UTC, submitted by Tom
"It was the only moment I heard regret slip into Otellini's voice during the several hours of conversations I had with him. 'The lesson I took away from that was, while we like to speak with data around here, so many times in my career I've ended up making decisions with my gut, and I should have followed my gut,' he said. 'My gut told me to say yes.'" The world would've been a much different place - Apple would have been less dependant on Samsung for its chips, which probably would've meant less money for Samsung to develop its Galaxy business.
Linked by Thom Holwerda on 05/16/13 21:41 UTC
Glass is getting some love at Google I/O as well. New applications have been released - Facebook, Twitter, Evernote, Elle, Tumblr, and CNN. Perhaps more interesting: the newly announced Google Glass Developer Kit will allow offline applications and direct hardware access - great for hacking and expanding Glass' potential. This kit will really allow hackers to put Glass through its paces.
Linked by Thom Holwerda on 05/16/13 17:04 UTC
"But Beck and Merrill decided that simply banning toxic players wasn't an acceptable solution for their game. Riot Games began experimenting with more constructive modes of player management through a formal player behavior initiative that actually conducts controlled experiments on its player base to see what helps reduce bad behavior. The results of that initiative have been shared at a lecture at the Massachusetts Institute of Technology and on panels at the Penny Arcade Expo East and the Game Developers Conference." Absolutely fascinating stuff. I'm a League of Legends player, and to be honest, the community isn't nearly as bad as some make it out to be. I'm happy Riot games has the guts to employ science to address the issue.
Linked by Thom Holwerda on 05/16/13 13:17 UTC
"Android and iOS, the number one and number two ranked smartphone operating systems worldwide, combined for 92.3% of all smartphone shipments during the first quarter of 2013 as Windows Phone crept past BlackBerry for 3rd place. According to the International Data Corporation Worldwide Quarterly Mobile Phone Tracker, Android smartphone vendors and Apple shipped a total of 199.5 million units worldwide during 1Q13, up 59.1% from the 125.4 million units shipped during 1Q12." Windows Phone doubles from a few to twice few, iOS loser market share as its growth is slower than that of the overall market. BlackBerry continues slide into irrelevance.
Linked by Thom Holwerda on 05/16/13 12:06 UTC
"According to the latest research from our Wireless Smartphone Strategies service, global Android smartphone profits reached US$5 billion in total during the first quarter of 2013. Samsung dominated and captured an impressive 95 percent share of all Android smartphone profits." Wow.
Linked by Thom Holwerda on 05/15/13 23:03 UTC
"During its Keynote today, Google announced new features coming to its flagship search function - you know, that thing we all started using Google for. VP Amit Singhal spent some time discussing what Google's search functionality will eventually morph into. Google's strategy is summarized by three words: answer, converse, and anticipate. Singhal explained that many of the pieces of these upcoming changes can already be seen in products that Google has recently introduced - namely, Google Knowledge Graph and Google Now, with perhaps a splash of Google Glass, too." I hold on to my hat every time Google changes Search. It's such a vital product in my daily life.More News »
Sponsored Links
Member since:
2008-08-11
Isn't the semaphore also a kernel-provided mechanism, which forces both processes to synchronize via kernel entries? Also, the usage of a shared-memory communication comes not for free as one has to establish the shared memory with each communication partner, allocate buffers in the shared memory, maybe allocate control packets, acknowledge completed messages for buffer reuse and maybe unblock the sender that wants to marshal the next message. From our experience with Genode, this pays off for bulk-data transfer but not for most RPCs with just a few register words of payload.
Modern microkernels like Fiasco.OC support fast inter-process communication with a user-level accessible part of the thread control block - UTCB - with a size of about 64 register words or something more. Processes marshal their message payload into the UTCB, the kernel copies from sender to receiver UTCB, and, finally, the receiver demarshals the data out of the UTCB as needed. Performance-wise this should fit the approach you described, the time for the copy operation is bounded by UTCB size, and there's no shared-memory establishment overhead as only the kernel accesses both UTCBs.