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
makefile.

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
zero.

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
hardware?)

Thanx in advance

Sven


--
Sven F├╝lster
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