

Digging out a linux threading regression - alcuadrado
http://timetobleed.com/digging-out-the-craziest-bug-you-never-heard-about-from-2008-a-linux-threading-regression/

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lifthrasiir
Copied from tl;dr: (Emphases in the original)

> This blog post will show how a fix for XFree86 and linuxthreads ended up
> causing a major threading regression _about 7 years_ after the fix was
> created.

> The regression was in `pthread_create`. Thread creation performed very
> slowly as the number of threads in a process increased. _This bug is present
> on CentOS 5.3 (and earlier) and other linux distros as well._

Actually, while it merits a (fine) blog post, it is far from being _the_
craziest as the original post title suggests. But what I find really important
is surely the following paragraph:

> It is also very possible that this bug impacted research done before _August
> 15, 2008_ (in the best case because Linux distro releases are slow) on
> building high performance threaded applications.

Research is hard since you may be affected with every possible cause unknown
to you.

~~~
ice799
I thought it was pretty crazy that a tweak to prevent XFree86 from breaking on
64bit systems + support for the ELF small code execution model would later
result in pthread_create overhead so large that creating threads on a P4 would
be as slow as creating threads on a 386.

But, hey, maybe it isn't that crazy to you.

------
gracemo
Love this bug! <http://www.ibiblio.org/harris/500milemail.html>

