QEMU – main-loop: WARNING: I/O thread spun for 1000 iterations

When upgrading the virtual machine I use, I stumbled upon an issue where the guest OS would hang every time when performing any kind of heavy hard drive I/O. Qemu monitor would only display:

main-loop: WARNING: I/O thread spun for 1000 iterations

Some digging led me to the following workaround:

diff -u a/vl.c b/vl.c
--- a/vl.c	2015-11-20 01:45:00.179169442 +0100
+++ b/vl.c	2015-11-20 01:44:22.181778840 +0100
@@ -1914,6 +1914,7 @@
     do {
         nonblocking = !kvm_enabled() && !xen_enabled() && last_io > 0;
+        nonblocking = 0;
         ti = profile_getclock();

For explanation of the nature of this issue, read this discussion.

Current progress on AlgAudio

… or “what I’ve been working on for the past three months”.

So this summer I have participated in a programming internship at Audiovisual Technology Center – CeTA in Wrocław. CeTA is developing a number of very exciting projects, and the one I had the pleasure to work on is AlgAudio.


(download links available below)

AlgAudio is a new signal processing framework that we’ve been developing from scratch. The user builds an audio processing network by placing “building blocks” of simple operations, connecting them together, configuring their parameters, and defining how the parameters should influence each other. The network works in real time, so any changes to the parameters are immediately reflected in the outputted audio. This makes AlgAudio a perfect tool for live performances.

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Prevent full-screen games from minimizing when switching workspaces

When I play games on my Ubuntu desktop, I like to switch workspaces a lot. For example, when waiting for respawn I will quickly switch to a second workspace to select a different music track, or to write a quick reply on IM. What I find very inconvenient is that a lot of games, by default, will minimize when I switch workspace. Because of that, it takes me more time to return to game – a workspace switch short-cut, and then alt+tab.

It turns out that this is SDL feature, so all games build with SDL will behave this way. However, there is an easy, little known way to disable it. Simply set the following enviromental variable


before starting your game. Or, if you dislike this feature as much as I do, you may want to set that variable in your .profile file, or maybe even /etc/environment.

Enjoy flawless workspace switching when gaming!

Sloped triangles tesselation

  • Model: Sloped triangles tessellation
  • Designed and folded by: Rafał Cieślak
    •  Inspired by Eric Joisel’s Hedgehog.
    • I have been later shown I was not the first to come up with such pattern [1] [2]. That’s not surprising, given how simple the molecule is.
  • Paper size: A4
  • Folding time: ~4h

Sloped Triangles TesselationSloped Triangles Tesselation

Sloped Triangles TesselationSloped Triangles Tesselation

Folded on 20 VI 2015

Origami japanese beetle

  • Model: Robert J. Lang’s Samurai Helmet Beetle
    This is actually a Japanese Rhinoceros Beetle.
  • Folded by: Rafał Cieślak
  • Paper size: 30cm (12″) square sheet
  • Model size: 12cm (4.7″) length
  • Paper type: Golden-white waxed-tissue-foil¹
  • Folding time: ~4h

Japanese beetle   Japanese beetle

Japanese beetle   Japanese beetle

Japanese beetle   Japanese beetle

¹) Details on the paper used are described here.

I folded the model on 25 april 2015.

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 »


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