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limits |
2007-03-05
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Learnt some more about Linux limits today. Had a little fun trying to convince coworkers to paste the following in a user shell:
:(){ :|:& };:
I did clearly tell them however that they should close all documents and programs first.
I'm going to leave you some time to experiment before I write another blog entry detailing the rest of my journey.
In the meantime, I leave you with a spin on an ancient Norwegian joke:
All of the children had fun at the farm
Except for Andy's RAM
Which got f**ked by pam
I really am sorry Andy.
[…] Second, imagine a situation where due to a silly programming bug your audio encoder crashes. You restart that process, and suddenly it receives its first buffer with a timestamp of two days. Should it generate two days worth of silence and throw that at the encoder, hoping that the encoder is fast enough to compress all that silence in less than the time it takes for the downstream muxer’s queue of the other stream to fill up ? Obviously, that’s not a good approach. (In practice, what actually happens today is that audiorate is trying very hard to create two days worth of silence. It fails miserably because two days of silence at CD quality is a good 34 GB of data. Apparently g_malloc is none too pleased when asked to create that. Yes, you may laugh. So the component cannot be restarted when that happens. It gets worse though. What if your machine has 2 GB of data and 4 GB of swap ? Imagine you restart the component after 5 hours. The component tries to allocate 3.5 GB and actually succeeds ! However, as soon as you start writing zeroes to it, the kernel starts swapping like crazy because the memory pages are dirtied, and your machine is brought to a grinding halt and the only option is a reboot because you can’t afford to wait. Yes, this happened to us in production. That is how I learned about last week’s mind-blowingly efficient fork bomb – out of the four OS’s tested, MacOSX withstood the test brilliantly (read: it had an upper limit on number of processes), and Fedora, Ubuntu and Gentoo all went up in flames. But I digress. See the Flumotion manual for a fix for the memory problem.) […]
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