Linked by Thom Holwerda on Sat 28th Jun 2008 22:09 UTC, submitted by diegocg
"Maybe I'm just naive, but designing a graphics API such that all image data had to be sent over a socket to another process every time the image needed to be drawn seems like complete idiocy. Unfortunately, that is precisely what the X Window System forces a program to do, and exactly what Cairo does when drawing images in Linux - a full copy of the image data, send to another process, no less, every time it is drawn. One would think there would be some room for improvement. Unsurprisingly, others felt the same way about X, and decided to write an extension, Xlib Shm or XShm for short, that allows images to placed in a shared memory segment from which the X server reads which allows the program to avoid the memory copy. GTK already makes use of the XShm extension, and it seems like a good idea to see if Gecko couldn't do the same."
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Member since:2005-07-06
I don't understand your point about the shared memory preventing hardware optimisation: all the extension says in that in the end the one who create the data must put it at this 'shared memory' location?
If the GPU can read or write at this memory location (depending on the operation of course), why couldn't there be hardware accelation?
RE[2]: Comment by SomeGuy
by SomeGuy on Sun 29th Jun 2008 21:13
in reply to "RE: Comment by SomeGuy"
Member since:2006-03-20
Because if you can't move the pixmap to fast video ram for accelerated hardware operations, you've already lost. Although just using XShmPutImage can sometimes be a win, it isn't always, because chances are you'll be copying or moving the memory anyways.
The X SHM extension -- the way it's normally used -- makes it very hard to do this efficiently, if not entirely impossible, so Xshm beats traditional XPutImage if you only care about a single blit, but if you're reusing the pixmap it can be a net loss, depending on your drivers (the better the drivers, the more of a loss it is)
In fact, it's so much worse that Exa (the new Xorg acceleration architecture) actually disables parts of the extension (shared pixmaps) so that it can properly accelerate 2d stuff.
News
Linked by Thom Holwerda on 05/19/13 23:15 UTC
"This is my NeXTstation Turbo Color booting the Mac System 7.1 Operating System using a hardware add-on called 'Daydream'. The Daydream has a Mac ROM and a few custom ICs in it and hooked up to the NeXTs DSP port. Turns your NeXT into a full fledged 68k powered Mac." So cool.
Linked by Thom Holwerda on 05/19/13 23:11 UTC, submitted by Drumhellar
"The NetBSD Project is pleased to announce NetBSD 6.1, the first feature update of the NetBSD 6 release branch. It represents a selected subset of fixes deemed important for security or stability reasons, as well as new features and enhancements. Please note that all fixes in the prior security/bugfix updates (NetBSD 6.0.1 and 6.0.2) are also in 6.1."
Linked by Thom Holwerda on 05/18/13 21:06 UTC
"At the end of a week in which Electronic Arts confirmed it wasn't developing a thing for the Wii U, one of the software engineers in EA Sports' Canada studio, in a series of since-deleted tweets, disparaged the console as 'crap' and suggested Nintendo should give up on hardware altogether. 'The Wii U is crap. Less powerful than an Xbox 360. Poor online/store. Weird tablet', tweeted Bob Summerwill, listed as a senior software engineer at EA Canada, in a reply to a tweet posting a link about EA's no-Wii U news. 'Nintendo are walking dead at this point'." The Wii U is turning into the 21st century's Virtual Boy.
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
Appfour 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.More News »
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Member since:
2006-03-20
Sockets are essentially a memcpy() in kernel. They're quite cheap when amortized over blitting the same image to screen repeatedly
Shm leads to hard synchronization issues, which could lead to messy pixmap stomping if the client/X server isn't careful.
But more importantly, the SHM data *must* be kept in the shared buffer. This doesn't sound so important until you realize that the image *doesn't* want to live in the shared buffer when it's being accelerated. what does this mean?
Well, if you're using the shm extension, you're essentially forcing the X server to draw in software (not that it's a change from the poorly accelerated proprietary drivers he was using, anyways.)
If you upload images and paint them repeatedly, the good old upload-over-a-socket allows X to put the pixmaps wherever it wants to get best performance. This is really why XSHM is discouraged these days.