Revert "OS-8005 bhyve memory pressure needs to target ARC better (#354)"
This reverts commit a6033573eedd94118d2b9e65f45deca0bf4b42f7.

@@ -18,11 +18,11 @@
  *
  * CDDL HEADER END
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright 2020 Joyent, Inc.
+ * Copyright (c) 2019, Joyent, Inc.
  * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
  * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
  * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2011, 2019, Delphix. All rights reserved.
  * Copyright (c) 2020, George Amanakis. All rights reserved.

@@ -4542,11 +4542,10 @@
         FMR_LOTSFREE,
         FMR_SWAPFS_MINFREE,
         FMR_PAGES_PP_MAXIMUM,
         FMR_HEAP_ARENA,
         FMR_ZIO_ARENA,
-        FMR_VIRT_MACHINE,       /* 'VM' seems ambiguous in this context */
 } free_memory_reason_t;
 
 int64_t last_free_memory;
 free_memory_reason_t last_free_reason;
 

@@ -4558,53 +4557,11 @@
 /*
  * Additional reserve of pages for swapfs.
  */
 int64_t arc_swapfs_reserve = 64;
 
-static volatile uint64_t arc_virt_machine_reserved;
-
 /*
- * XXX: A possible concern is that we allow arc_virt_machine_reserved to
- * get so large that we cause the arc to perform a lot of additional
- * work to keep the arc extremely small. We may want to set limits to
- * the size of arc_virt_machine_reserved and disallow reservations
- * beyond that limit.
- */
-int
-arc_virt_machine_reserve(size_t pages)
-{
-        uint64_t newv;
-
-        newv = atomic_add_64_nv(&arc_virt_machine_reserved, pages);
-
-        /*
-         * Since arc_virt_machine_reserved effectively lowers arc_c_max
-         * as needed for vmm memory, if this request would put the arc
-         * under arc_c_min, we reject it.  arc_c_min should be a value that
-         * ensures reasonable performance for non-VMM stuff, as well as keep
-         * us from dipping below lotsfree, which could trigger the pager
-         * (and send the system toa grinding halt while it pages).
-         *
-         * XXX: This is a bit hacky and might be better done w/ a mutex
-         * instead of atomic ops.
-         */
-        if (newv + arc_c_min > arc_c_max) {
-                atomic_add_64(&arc_virt_machine_reserved, -(int64_t)pages);
-                return (ENOMEM);
-        }
-
-        zthr_wakeup(arc_reap_zthr);
-        return (0);
-}
-
-void
-arc_virt_machine_release(size_t pages)
-{
-        atomic_add_64(&arc_virt_machine_reserved, -(int64_t)pages);
-}
-
-/*
  * Return the amount of memory that can be consumed before reclaim will be
  * needed.  Positive if there is sufficient free memory, negative indicates
  * the amount of memory that needs to be freed up.
  */
 static int64_t

@@ -4663,21 +4620,10 @@
         if (n < lowest) {
                 lowest = n;
                 r = FMR_PAGES_PP_MAXIMUM;
         }
 
-        /*
-         * Check that we have enough memory for any virtual machines that
-         * are running or starting. We add desfree to keep us out of
-         * particularly dire circumstances.
-         */
-        n = PAGESIZE * (availrmem - arc_virt_machine_reserved - desfree);
-        if (n < lowest) {
-                lowest = n;
-                r = FMR_VIRT_MACHINE;
-        }
-
 #if defined(__i386)
         /*
          * If we're on an i386 platform, it's possible that we'll exhaust the
          * kernel heap space before we ever run out of available physical
          * memory.  Most checks of the size of the heap_area compare against