[Barrelfish-users] page size in barrelfish virtual memory system

[Xiaowen Wang]

Hi,

Thanks for your reply.

For my problem, my architecture requires 64KB small page size, much larger than 4KB, so that consumes much memory when running the function of "spawn_module(...)" (startup.c:174), and I noticed that in this function, when it allocates memory for "slot_alloc_cn0", for example, it requests "OBJBITS_CTE + SLOT_ALLOC_CNODE_BITS" amount of memory, in which "SLOT_ALLOC_CNODE_BITS" is defined as "DEFAULT_CNODE_BITS * 2" (barrelfish/init.h:91), which it is too big in my case. And the number of allocated memory grows exponentially with the page size. What it is the desired meaning of the "* 2"?

What is the meaning of this three CNodes of "slot_alloc_cn0", "slot_alloc_cn1" and "slot_alloc_cn2"?


Best regards,
Xiaowen Wang


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On Wed, Oct 10, 2012 at 01:02:27AM +0000, Xiaowen Wang wrote:
> Recently I am porting Barrelfish to another architecture. I noticed that
> Barrelfish has "init" program which requires 4K pages for its virtuall memory.
> so does Barrelfish only allow 4K pages? or is it possible to change the size of
> "BASE_PAGE_SIZE"?

In principle you should be able to set BASE_PAGE_SIZE and friends (i.e.,
BASE_PAGE_BITS, etc.) to a different value for your architecture. In
practice, however, since all the architectures we support have 4K
page sizes, this has not been tested and you might get some surprises.  I
would think that if the new value is reasonable (e.g., not too small),
most of the problems --if any-- would be easy to fix.

cheers,
Kornilios.


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