[GSoC2012]Use hash or map in POSIX keys

Ashi ashi08104 at gmail.com
Tue Apr 24 15:05:20 UTC 2012

Hi, all. My project is use hash or map in POSIX keys. Here is the
description of my project:

The objective of this project is reducing the memory overhead in  the
implementation of POSIX keys without adding any extra lookup overhead
by some proper hash or map algorithm. This feature is required by two
first, the POSIX key area is not properly extended when the number of
threads is increased(dynamically created) if POSIX threads are
configured as "unlimited", which is a known bug.
Second, extra memory is reserved in keys for each thread or task in
current implementation, which can be heavy memory overhead when keys
increase since key can be dynamically created.
Concretely, it changes the POSIX key part of RTEMS, which is static
array in existing implementation, to a kind of dynamic data structure,
which can be hash or map. Proper hash or map algorithm will be
selected so that there is no excessive lookup overhead compared with
existing implementation. Besides fix the POSIX key bug as mentioned
above, I think RTEMS can also benefit from this project by applying
this change to some similar context in RTEMS, such as in the device
driver interface and shell command lookup. Because nothing special is
needed, sparc/sis will be used as testing target during whole project.

I have a personal blog[1], nothing about this project has updated yet
until now though, but I think I will update information about this
projects during GSoC2012. So I also give link to my blog here. Thanks
for your attention!

Best regards!
Zhongwei Yao


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