Need some help in understanding sparsemem.

[naren.mehra@gmail.com]

Hi,

I am trying to understand the sparsemem implementation in linux for
NUMA/multiple node systems.

>From the available documentation and the sparsemem patches, I am able
to make out that sparsemem divides memory into different sections and
if the whole section contains a hole then its marked as invalid
section and if some pages in a section form a hole then those pages
are marked reserved. My issue is that this classification, I am not
able to map it to the code.

e.g. from arch specific code, we call memory_present()  to prepare a
list of sections in a particular node. but unable to find where
exactly some sections are marked invalid because they contain a hole.

Can somebody tell me where in the code are we identifying sections as
invalid and where we are marking pages as reserved.

Pls correct me, if I am wrong in my understanding.
Also, If theres any article or writeup on sparsemem, pls point me to that.

I apologize, if I have posted this mail on the wrong mailing list, in
that case, pls let me know the correct forum to ask this question.

Regards,
Naren

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