Multi-OS gaming w/o dual-booting: Excelent graphics performance in a VM with VGA passthrough

Note: This articles is a technology/technique outline, not a detailed guide and not a how-to. It explains what is VGA passthrough, why you might be interested in it, and where to start.

Even with the current abundance of Linux native games (both indies and AAAs), with WINE reliably running almost any not-so-new software, many gamers who use Linux on a daily basis tend to switch to Windows for playing games. Regardless of one’s attitude towards non-free software, it has to be admitted that if you wish to try out some of the newest titles, you have no other choice than running them on a Windows installation. This is why so many gamers dual-boot: having installed two operating systems on the same machine and using Windows for playing games and Linux for virtually anything else, they limit their usage of Microsoft’s OS for gaming only. This popular technique seems handy – you get the luxury of using a Linux, and the gaming performance of Windows.

But dual-booting is annoying because of the need of reboot to switch your context. Need to IM your friend while playing? Save your game, shut down Windows, reboot to Linux, launch IM, reboot to Windows, load your game. Switching takes a long time, is inconvenient, and therefore the player may feel discouraged to do so.

What if you could run both operating systems at once? That’s nothing new, run a virtual machine in your Linux, install Windows within it, and voilà! But a virtual machine is no good for gaming, the performance will be utter cr terrible. Playing chess might work, but any 3D graphics won’t do because of the lack of hardware acceleration. The VM emulates a simple graphics adapter to display it’s output in a window of the host OS.

And that is where VGA passthrough comes in, and solves this issue.

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Origami butterfly

  • Model: Robert J. Lang’s Butterfly
  • Folded by: Rafał Cieślak
  • Paper size: 36cm (14″) square sheet
  • Model size: 15cm (6″) wing span
  • Paper type: Waxed-tissue-foil¹
  • Folding time: ~5h

Butterfly   Butterfly

Butterfly   Butterfly Read the rest of this entry »

C++11: std::threads managed by a designated class

Recently I have noticed an unobvious problem that may appear when using std::threads as class fields. I believe it is more than likely to meet if one is not careful enough when implementing C++ classes, due to it’s tricky nature. Also, its solution provides an elegant example of what has to be considered when working with threads in object-oriented C++, therefore I decided to share it.

Consider a scenario where we would like to implement a class that represents a particular thread activity. We would like it to:

  • start a new thread it manages when an instance is constructed
  • stop it when it is destructed

I will present the obvious implementation, explain the problem with it, and describe how to deal with it.

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A few drawings

I find drawing relaxing. Here are some images I recently draw using Inkscape:

blue1redcat1mamooth1Each took about 2-3 evenings to draw. They work pretty well as wallpapers, hi-res versions can be downloaded by clicking on an image.

I do not have much spare time on evenings, so it is rare for me to spend them drawing animals. I do, however, enjoy the results a lot. Vector graphics are fun!

Programowanie zespołowe na wakacje

Picture taken from yugioh.wikia.com, where it was published under the terms of the CC-BY-SA license.

tl;dr: Szukam niezaawansowanych informatyków zainteresowanych zdobywaniem doświadczenia, chętnych do dobrowolnego programowania w prowadzonym przeze mnie zespole w trakcie wakacji, oferując ze swojej strony potrzebne szkolenia i szeroko pojętą pomoc.

UPDATE: Zainteresowanie projektem okazało się większe, niż się spodziewałem; w ciągu kilka dni udało się skompletować całkiem rozsądną 7-osobową ekipę. Ze względu na moje ograniczone możliwości, nie jestem w stanie przyjąć więcej osób.

Wysoka temperatura, koniec sesji, przesilenie letnie, różne są oznaki nadchodzących wakacji. Dla mnie wakacje to przede wszystkim spora ilość czasu wolnego. Mam w zwyczaju poświęcać ten czas nie tylko na coroczny wypoczynek, ale też by we własnym zakresie poszerzać umiejętności, zgodnie z zainteresowaniami.

W praktyce oznacza to, że w wakacje dużo programuję dla własnej przyjemności. Czasem są to rzeczy pożyteczne światu, czasem jest to eksperymentowanie z różnymi technologiami; czasami piszę samotnie, czasami w zespole. W każdym przypadku wiąże się to ze zdobywaniem doświadczenia.

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Dynamic linker tricks: Using LD_PRELOAD to cheat, inject features and investigate programs

This post assumes some basic C skills.

Linux puts you in full control. This is not always seen from everyone’s perspective, but a power user loves to be in control. I’m going to show you a basic trick that lets you heavily influence the behavior of most applications, which is not only fun, but also, at times, useful.

A motivational example

Let us begin with a simple example. Fun first, science later.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(){
  srand(time(NULL));
  int i = 10;
  while(i--) printf("%d\n",rand()%100);
  return 0;
}

Simple enough, I believe. I compiled it with no special flags, just

gcc random_num.c -o random_num

I hope the resulting output is obvious – ten randomly selected numbers 0-99, hopefully different each time you run this program.

Now let’s pretend we don’t really have the source of this executable. Either delete the source file, or move it somewhere – we won’t need it. We will significantly modify this programs behavior, yet without touching it’s source code nor recompiling it.

For this, lets create another simple C file:

int rand(){
    return 42; //the most random number in the universe
}

We’ll compile it into a shared library.

gcc -shared -fPIC unrandom.c -o unrandom.so

So what we have now is an application that outputs some random data, and a custom library, which implements the rand() function as a constant value of 42.  Now… just run random_num this way, and watch the result:

LD_PRELOAD=$PWD/unrandom.so ./random_nums

If you are lazy and did not do it yourself (and somehow fail to guess what might have happened), I’ll let you know – the output consists of ten 42’s.

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e4rat – decreasing bootup time on HDD drives

This time I will describe how to set up e4rat in order to speed your Ubuntu’s boot time. Let’s begin with some motivation: my netbook used to boot-up in ~40 seconds. Using e4rat, it takes ~10-15 seconds. Impressive, isn’t it? Let’s see how does this trick work, and I’ll teach you how to enable it on your machine.

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