Redo the page table page allocation on MIPS, as suggested by

alc@.

The UMA zone based allocation is replaced by a scheme that creates
a new free page list for the KSEG0 region, and a new function
in sys/vm that allocates pages from a specific free page list.

This also fixes a race condition introduced by the UMA based page table
page allocation code. Dropping the page queue and pmap locks before
the call to uma_zfree, and re-acquiring them afterwards  will introduce
a race condtion(noted by alc@).

The changes are :
- Revert the earlier changes in MIPS pmap.c that added UMA zone for
page table pages.
- Add a new freelist VM_FREELIST_HIGHMEM to MIPS vmparam.h for memory that
is not directly mapped (in 32bit kernel). Normal page allocations will first
try the HIGHMEM freelist and then the default(direct mapped) freelist.
- Add a new function 'vm_page_t vm_page_alloc_freelist(int flind, int
order, int req)' to vm/vm_page.c to allocate a page from a specified
freelist. The MIPS page table pages will be allocated using this function
from the freelist containing direct mapped pages.
- Move the page initialization code from vm_phys_alloc_contig() to a
new function vm_page_alloc_init(), and use this function to initialize
pages in vm_page_alloc_freelist() too.
- Split the  function vm_phys_alloc_pages(int pool, int order) to create
vm_phys_alloc_freelist_pages(int flind, int pool, int order), and use
this function from both vm_page_alloc_freelist() and vm_phys_alloc_pages().

Reviewed by:	alc

1 files changed, 14 insertions, 4 deletions

diff --git a/sys/mips/include/vmparam.h b/sys/mips/include/vmparam.h
index 6f45244..e09f6a2 100644
--- a/sys/mips/include/vmparam.h
+++ b/sys/mips/include/vmparam.h
@@ -125,7 +125,6 @@
 #define	VM_NRESERVLEVEL		0
 #endif
 
-
 /* virtual sizes (bytes) for various kernel submaps */
 #ifndef VM_KMEM_SIZE
 #define	VM_KMEM_SIZE		(12 * 1024 * 1024)
@@ -174,13 +173,24 @@
 #define	VM_FREEPOOL_DIRECT	1
 
 /*
- * we support 1 free list:
+ * we support 2 free lists:
  *
- *	- DEFAULT for all systems
+ *	- DEFAULT for direct mapped (KSEG0) pages.
+ *	  Note: This usage of DEFAULT may be misleading because we use
+ *	  DEFAULT for allocating direct mapped pages. The normal page
+ *	  allocations use HIGHMEM if available, and then DEFAULT. 
+ *	- HIGHMEM for other pages 
  */
-
+#ifdef __mips_n64
 #define	VM_NFREELIST		1
 #define	VM_FREELIST_DEFAULT	0
+#else
+#define	VM_NFREELIST		2
+#define	VM_FREELIST_DEFAULT	1
+#define	VM_FREELIST_HIGHMEM	0
+#define	VM_FREELIST_DIRECT	VM_FREELIST_DEFAULT
+#define	VM_HIGHMEM_ADDRESS	((vm_paddr_t)0x20000000)
+#endif
 
 /*
  * The largest allocation size is 1MB.