DragonFly bugs List (threaded) for 2003-09
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Re: contigmalloc for low address in SI_SUB_KMEM
On Wed, Sep 03, 2003 at 09:22:47AM -0700, Matthew Dillon wrote:
> I am almost certain that the problem is that all of the low (ISA DMA)
> memory is being allocated due to the large slab cluster size.
>
> The solution is to try to figure out why that is occuring. Long ago
> we 'fixed' FreeBSD by having it allocate higher physical addresses
> first, leaving lower ones available for contigmalloc during booting.
> Somehow this feature must have gotten broken.
I'm slowly beginning to understand what's happening there; pmap_init()
tries to allocate about 1.7Mbytes of memory block via kmem_alloc(),
and as kmem_alloc() calls vm_page_grab() with VM_ALLOC_ZERO, lower
addresses are consumed first(because free blocks are queued in descending
order at the bottom of vm_page_startup(), I suppose).
My workaround at the moment is to allocate some amount of memory by
kmem_alloc() in vm_mem_init() before pmap_init(), and mem_free() it
afterwards.
Index: vm_init.c
===================================================================
RCS file: /home/source/dragonfly/cvs/src/sys/vm/vm_init.c,v
retrieving revision 1.4
diff -u -r1.4 vm_init.c
--- vm_init.c 27 Aug 2003 01:43:08 -0000 1.4
+++ vm_init.c 9 Sep 2003 16:41:47 -0000
@@ -95,11 +95,15 @@
* The start and end address of physical memory is passed in.
*/
+extern vm_map_t kernel_map;
+
/* ARGSUSED*/
static void
vm_mem_init(dummy)
void *dummy;
{
+ vm_offset_t m;
+ vm_size_t size = 0x10000;
/*
* Initializes resident memory structures. From here on, all physical
* memory is accounted for, and we use only virtual addresses.
@@ -114,6 +118,8 @@
vm_map_startup();
kmem_init(virtual_avail, virtual_end);
kmem_cpu_init();
+ m = kmem_alloc(kernel_map, size);
pmap_init(avail_start, avail_end);
+ kmem_free(kernel_map, m, size);
vm_pager_init();
}
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