svn commit: r212784 - head/sys/amd64/include

[Andriy Gapon]

Author: avg
Date: Fri Sep 17 07:36:32 2010
New Revision: 212784
URL: http://svn.freebsd.org/changeset/base/212784

Log:
  amd64: reduce VM_KMEM_SIZE_SCALE to 1 allowing kernel to use more memory
  
  KVA space is abundant on amd64, so there is no reason to limit kernel
  map size to a fraction of available physical memory.  In fact, it could
  be larger than physical memory.
  
  This should help with memory auto-tuning for ZFS and shouldn't affect
  other workloads.
  This should reduce number of circumstances for "kmem_map too small"
  panics, but probably won't eliminate them entirely due to potential kmem
  fragmentation.
  
  In fact, you might want/need to limit maximum ARC size after this commit
  if you need to resrve more memory for applications.
  
  This change was discussed on arch@ and nobody said "don't do it".
  
  MFC after:	6 weeks

Modified:
  head/sys/amd64/include/vmparam.h

Modified: head/sys/amd64/include/vmparam.h
==============================================================================
--- head/sys/amd64/include/vmparam.h	Fri Sep 17 07:34:50 2010	(r212783)
+++ head/sys/amd64/include/vmparam.h	Fri Sep 17 07:36:32 2010	(r212784)
@@ -205,7 +205,7 @@
  * is the total KVA space allocated for kmem_map.
  */
 #ifndef VM_KMEM_SIZE_SCALE
-#define	VM_KMEM_SIZE_SCALE	(3)
+#define	VM_KMEM_SIZE_SCALE	(1)
 #endif
 
 /*