[src/trunk]: src/sys/kern rework boundary-tag reserve calculation, make it mo...

[para <para%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d92e73233a48
branches:  trunk
changeset: 781345:d92e73233a48
user:      para <para%NetBSD.org@localhost>
date:      Sat Sep 01 12:28:58 2012 +0000

description:
rework boundary-tag reserve calculation, make it more precise.
add comment about the rational behind the sizing of certain vars
used by allocation and bootstrap.
as requested by yamt@

diffstat:

 sys/kern/subr_vmem.c |  30 ++++++++++++++++++++----------
 1 files changed, 20 insertions(+), 10 deletions(-)

diffs (74 lines):

diff -r 23048a8f01a7 -r d92e73233a48 sys/kern/subr_vmem.c
--- a/sys/kern/subr_vmem.c      Sat Sep 01 12:19:32 2012 +0000
+++ b/sys/kern/subr_vmem.c      Sat Sep 01 12:28:58 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_vmem.c,v 1.74 2012/07/30 17:49:24 njoly Exp $     */
+/*     $NetBSD: subr_vmem.c,v 1.75 2012/09/01 12:28:58 para Exp $      */
 
 /*-
  * Copyright (c)2006,2007,2008,2009 YAMAMOTO Takashi,
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_vmem.c,v 1.74 2012/07/30 17:49:24 njoly Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_vmem.c,v 1.75 2012/09/01 12:28:58 para Exp $");
 
 #if defined(_KERNEL)
 #include "opt_ddb.h"
@@ -241,13 +241,23 @@
 #else /* defined(_KERNEL) */
 
 #define        xmalloc(sz, flags) \
-    kmem_alloc(sz, ((flags) & VM_SLEEP) ? KM_SLEEP : KM_NOSLEEP);
-#define        xfree(p, sz)            kmem_free(p, sz);
+    kmem_intr_alloc(sz, ((flags) & VM_SLEEP) ? KM_SLEEP : KM_NOSLEEP);
+#define        xfree(p, sz)            kmem_intr_free(p, sz);
 
-#define BT_MINRESERVE 6
+/*
+ * Memory for arenas initialized during bootstrap.
+ * There is memory for STATIC_VMEM_COUNT bootstrap arenas.
+ *
+ * BT_RESERVE calculation:
+ * we allocate memory for boundry tags with vmem, therefor we have
+ * to keep a reserve of bts used to allocated memory for bts. 
+ * This reserve is 4 for each arena involved in allocating vmems memory.
+ * BT_MAXFREE: don't cache excessive counts of bts in arenas
+ */
+#define STATIC_VMEM_COUNT 4
+#define STATIC_BT_COUNT 200
+#define BT_MINRESERVE 4
 #define BT_MAXFREE 64
-#define STATIC_VMEM_COUNT 5
-#define STATIC_BT_COUNT 200
 /* must be equal or greater then qcache multiplier for kmem_va_arena */
 #define STATIC_QC_POOL_COUNT 8
 
@@ -283,7 +293,7 @@
        int i;
 
        mutex_enter(&vmem_btag_lock);
-       if (vmem_btag_freelist_count > (BT_MINRESERVE * 16)) {
+       if (vmem_btag_freelist_count > 0) {
                mutex_exit(&vmem_btag_lock);
                return 0;
        }
@@ -325,7 +335,7 @@
        VMEM_LOCK(vm);
        mutex_enter(&vmem_btag_lock);
        while (!LIST_EMPTY(&vmem_btag_freelist) &&
-           vm->vm_nfreetags < (BT_MINRESERVE * 2)) {
+           vm->vm_nfreetags <= BT_MINRESERVE) {
                bt = LIST_FIRST(&vmem_btag_freelist);
                LIST_REMOVE(bt, bt_freelist);
                LIST_INSERT_HEAD(&vm->vm_freetags, bt, bt_freelist);
@@ -349,7 +359,7 @@
        bt_t *bt;
 again:
        VMEM_LOCK(vm);
-       if (vm->vm_nfreetags < BT_MINRESERVE &&
+       if (vm->vm_nfreetags <= BT_MINRESERVE &&
            (flags & VM_POPULATING) == 0) {
                VMEM_UNLOCK(vm);
                if (bt_refill(vm, VM_NOSLEEP | VM_INSTANTFIT)) {