Early memory allocation

mx at ...19... mx at ...19...
Fri Jul 3 13:59:25 CEST 2009

Hi all,

first of all thank you Christian for the quick bugfix concerning the dde/usb

This time, I have a question related to the allocation of memory during system
startup. At the moment, I'm just working with qemu/ l4ka-pistachio, and I've
noticed that the initial memory allcation ("Trying to allocate 4K pages from
sigma0") requests over 100MB, and this allocation takes about 3 seconds on my
machine (without kqemu acceleration).

In core/platform.cc I saw, that you ask sigma0 for the entire amount of memory
it has concerning this page size and that you also memset the returned memory to

When playing around with that, I saw that omitting the zeroing does not seem to
have any impact on the running system (I only have a dde driver running...).

I also saw that I may - for a start - limit the memory allocation to a much
smaller size. This involved a much better startup performance.

So I wonder why the zeroing is needed, and I'd like to know if your memory
management allowed for subsequent allocations from sigma0, so that I could save
some startup time and allocate the remaining memory later.

(Is this question - from your point of view - worth the investigation at all? Or
is the delay only related to my slow qemu having no impact on an average

Thanx in advance


Sven F├╝lster
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