From d91722fb27d3fd6be8cb2e66f047dee566d216da Mon Sep 17 00:00:00 2001
From: Jeff Roberson <jeff@FreeBSD.org>
Date: Mon, 19 Aug 2013 23:02:39 +0000
Subject: [PATCH]  - Use an arbitrary but reasonably large import size for kva
 on architectures    that don't support superpages.  This keeps the number of
 spans and internal    fragmentation lower.  - When the user asks for
 alignment from vmem_xalloc adjust the imported size    by 2*align to be
 certain we can satisfy the allocation.  This comes at    the expense of
 potential failures when the backend can't supply enough    memory but could
 supply the requested size and alignment.

Sponsored by:	EMC / Isilon Storage Division
---
 sys/kern/subr_vmem.c | 11 +++++++++--
 sys/vm/vm_init.c     |  3 ++-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/sys/kern/subr_vmem.c b/sys/kern/subr_vmem.c
index cff28b7947e..fc431e64279 100644
--- a/sys/kern/subr_vmem.c
+++ b/sys/kern/subr_vmem.c
@@ -758,6 +758,7 @@ vmem_add1(vmem_t *vm, vmem_addr_t addr, vmem_size_t size, int type)
 	bt_t *btfree;
 
 	MPASS(type == BT_TYPE_SPAN || type == BT_TYPE_SPAN_STATIC);
+	MPASS((size & vm->vm_quantum_mask) == 0);
 
 	btspan = bt_alloc(vm);
 	btspan->bt_type = type;
@@ -805,7 +806,7 @@ vmem_destroy1(vmem_t *vm)
 }
 
 static int
-vmem_import(vmem_t *vm, vmem_size_t size, int flags)
+vmem_import(vmem_t *vm, vmem_size_t size, vmem_size_t align, int flags)
 {
 	vmem_addr_t addr;
 	int error;
@@ -813,6 +814,12 @@ vmem_import(vmem_t *vm, vmem_size_t size, int flags)
 	if (vm->vm_importfn == NULL)
 		return EINVAL;
 
+	/*
+	 * To make sure we get a span that meets the alignment we double it
+	 * and add the size to the tail.  This slightly overestimates.
+	 */
+	if (align != vm->vm_quantum_mask + 1)
+		size = (align * 2) + size;
 	size = roundup(size, vm->vm_import_quantum);
 
 	/*
@@ -1157,7 +1164,7 @@ vmem_xalloc(vmem_t *vm, const vmem_size_t size0, vmem_size_t align,
 		 * imported region.  It is up to the user to specify the
 		 * import quantum such that it can satisfy any allocation.
 		 */
-		if (vmem_import(vm, size, flags) == 0)
+		if (vmem_import(vm, size, align, flags) == 0)
 			continue;
 
 		/*
diff --git a/sys/vm/vm_init.c b/sys/vm/vm_init.c
index 7ab1ee04164..0a381d03aef 100644
--- a/sys/vm/vm_init.c
+++ b/sys/vm/vm_init.c
@@ -156,7 +156,8 @@ vm_mem_init(dummy)
 #if VM_NRESERVLEVEL > 0
 	    1 << (VM_LEVEL_0_ORDER + PAGE_SHIFT));
 #else
-	    PAGE_SIZE);
+	    /* On non-superpage architectures want large import sizes. */
+	    PAGE_SIZE * 1024);
 #endif
 
 	kmem_init_zero_region();