Actually, this question is redundant and arises because of a lack of
understanding of the way memlists work. I wonder if someone could step me
through the way things work here...
I'm trying to get my mind around the use of memlists in the startup code. I've
modeled the System z code from the sun4 base.
I have three memory lists
struct memlist *phys_install; // list of memory making up the physical storage
struct memlist *phys_avail; // list of memory available for use
struct memlist *virt_avail; // list of virtual memory available for use
There is also what appears to be an anchor:
static struct memlist *memlist;
My code determines the real storage configuration: number and size of chunks
(usually one but System z does support discontiguous real memory). From this I
should create the phys_install memory list. System z has not bootops etc. which
means no boot memlist structures that need copying like sparc.
To create the memory list I'm doing:
phys_install = ndata_alloc(&ndata, nMemChunk * sizeof(memlist), sizeof(long));
for (i_Chunk = 0; i_Chunk < nMemChunk; i_Chunk++)
memlist_add((uintptr_t) sysMemory[i_Chunk].start, sysMemory[i_Chunk].len,
&phys_install, &phys_install);
Which, if my understanding is correct, will create a memory list that describes
the physical memory installed. However, I don't believe this is correct but I'm
not sure why.
After setting up all my kernel structures etc. I have real memory that's
unallocated which I can then add to the phys_avail memlist. This, I believe,
describes real memory that is usable by the system. This storage may be
comprised of discontiguous areas in the system (gaps between various areas or
the vast expanse of unused memory from the end of kernel used areas to the top
of real memory). I then create the phys_avail memlist by calling memlist_add to
add these discontiguous areas.
Now the code allocates a memspace area that appears to have enough room for
many memlist entries. The code then states:
memlist = (struct memlist *) memspace;
phys_avail = memlist;
and there can be a sequence of memlist_add's to add the discontiguous pages to
the memlist list. However, I'm not sure I'm initializing the list correctly as
the 1st memlist_add works but subsequent ones fail because it claims the list
is "munged" (from memlist_insert).
I'm not sure as to the purpose of the struct memlist variable called "memlist"
and how it is used by the rest of the memory management system.
Is there a "OpenSolaris Memlist Guide for Dummies"?
Neale
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