From 2e47807c21e3b3155f53059c21bc3196a45ed160 Mon Sep 17 00:00:00 2001
From: Jeff Roberson <jeff@FreeBSD.org>
Date: Tue, 28 Nov 2017 23:40:54 +0000
Subject: Eliminate kmem_arena and kmem_object in preparation for further NUMA
 commits.

The arena argument to kmem_*() is now only used in an assert.  A follow-up
commit will remove the argument altogether before we freeze the API for the
next release.

This replaces the hard limit on kmem size with a soft limit imposed by UMA.  When
the soft limit is exceeded we periodically wakeup the UMA reclaim thread to
attempt to shrink KVA.  On 32bit architectures this should behave much more
gracefully as we exhaust KVA.  On 64bit the limits are likely never hit.

Reviewed by:	markj, kib (some objections)
Discussed with:	alc
Tested by:	pho
Sponsored by:	Netflix / Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D13187
---
 sys/kern/subr_vmem.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

(limited to 'sys/kern/subr_vmem.c')

diff --git a/sys/kern/subr_vmem.c b/sys/kern/subr_vmem.c
index 4dd4fb8eff1e..5b88a3f69cac 100644
--- a/sys/kern/subr_vmem.c
+++ b/sys/kern/subr_vmem.c
@@ -137,6 +137,7 @@ struct vmem {
 	int			vm_nbusytag;
 	vmem_size_t		vm_inuse;
 	vmem_size_t		vm_size;
+	vmem_size_t		vm_limit;
 
 	/* Used on import. */
 	vmem_import_t		*vm_importfn;
@@ -228,11 +229,11 @@ static uma_zone_t vmem_bt_zone;
 
 /* boot time arena storage. */
 static struct vmem kernel_arena_storage;
-static struct vmem kmem_arena_storage;
 static struct vmem buffer_arena_storage;
 static struct vmem transient_arena_storage;
+/* kernel and kmem arenas are aliased for backwards KPI compat. */
 vmem_t *kernel_arena = &kernel_arena_storage;
-vmem_t *kmem_arena = &kmem_arena_storage;
+vmem_t *kmem_arena = &kernel_arena_storage;
 vmem_t *buffer_arena = &buffer_arena_storage;
 vmem_t *transient_arena = &transient_arena_storage;
 
@@ -254,11 +255,11 @@ bt_fill(vmem_t *vm, int flags)
 	VMEM_ASSERT_LOCKED(vm);
 
 	/*
-	 * Only allow the kmem arena to dip into reserve tags.  It is the
+	 * Only allow the kernel arena to dip into reserve tags.  It is the
 	 * vmem where new tags come from.
 	 */
 	flags &= BT_FLAGS;
-	if (vm != kmem_arena)
+	if (vm != kernel_arena)
 		flags &= ~M_USE_RESERVE;
 
 	/*
@@ -615,22 +616,22 @@ vmem_bt_alloc(uma_zone_t zone, vm_size_t bytes, uint8_t *pflag, int wait)
 {
 	vmem_addr_t addr;
 
-	*pflag = UMA_SLAB_KMEM;
+	*pflag = UMA_SLAB_KERNEL;
 
 	/*
 	 * Single thread boundary tag allocation so that the address space
 	 * and memory are added in one atomic operation.
 	 */
 	mtx_lock(&vmem_bt_lock);
-	if (vmem_xalloc(kmem_arena, bytes, 0, 0, 0, VMEM_ADDR_MIN,
+	if (vmem_xalloc(kernel_arena, bytes, 0, 0, 0, VMEM_ADDR_MIN,
 	    VMEM_ADDR_MAX, M_NOWAIT | M_NOVM | M_USE_RESERVE | M_BESTFIT,
 	    &addr) == 0) {
-		if (kmem_back(kmem_object, addr, bytes,
+		if (kmem_back(kernel_object, addr, bytes,
 		    M_NOWAIT | M_USE_RESERVE) == 0) {
 			mtx_unlock(&vmem_bt_lock);
 			return ((void *)addr);
 		}
-		vmem_xfree(kmem_arena, addr, bytes);
+		vmem_xfree(kernel_arena, addr, bytes);
 		mtx_unlock(&vmem_bt_lock);
 		/*
 		 * Out of memory, not address space.  This may not even be
@@ -835,7 +836,7 @@ vmem_import(vmem_t *vm, vmem_size_t size, vmem_size_t align, int flags)
 	int error;
 
 	if (vm->vm_importfn == NULL)
-		return EINVAL;
+		return (EINVAL);
 
 	/*
 	 * To make sure we get a span that meets the alignment we double it
@@ -845,6 +846,9 @@ vmem_import(vmem_t *vm, vmem_size_t size, vmem_size_t align, int flags)
 		size = (align * 2) + size;
 	size = roundup(size, vm->vm_import_quantum);
 
+	if (vm->vm_limit != 0 && vm->vm_limit < vm->vm_size + size)
+		return (ENOMEM);
+
 	/*
 	 * Hide MAXALLOC tags so we're guaranteed to be able to add this
 	 * span and the tag we want to allocate from it.
@@ -856,7 +860,7 @@ vmem_import(vmem_t *vm, vmem_size_t size, vmem_size_t align, int flags)
 	VMEM_LOCK(vm);
 	vm->vm_nfreetags += BT_MAXALLOC;
 	if (error)
-		return ENOMEM;
+		return (ENOMEM);
 
 	vmem_add1(vm, addr, size, BT_TYPE_SPAN);
 
@@ -977,6 +981,15 @@ vmem_set_import(vmem_t *vm, vmem_import_t *importfn,
 	VMEM_UNLOCK(vm);
 }
 
+void
+vmem_set_limit(vmem_t *vm, vmem_size_t limit)
+{
+
+	VMEM_LOCK(vm);
+	vm->vm_limit = limit;
+	VMEM_UNLOCK(vm);
+}
+
 void
 vmem_set_reclaim(vmem_t *vm, vmem_reclaim_t *reclaimfn)
 {
@@ -1009,6 +1022,7 @@ vmem_init(vmem_t *vm, const char *name, vmem_addr_t base, vmem_size_t size,
 	vm->vm_quantum_shift = flsl(quantum) - 1;
 	vm->vm_nbusytag = 0;
 	vm->vm_size = 0;
+	vm->vm_limit = 0;
 	vm->vm_inuse = 0;
 	qc_init(vm, qcache_max);
 
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