[src/trunk]: src/lib/libkvm use a binary search in _kvm_pa2off(). this helps...

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

details:   https://anonhg.NetBSD.org/src/rev/8b7b672f30fd
branches:  trunk
changeset: 745611:8b7b672f30fd
user:      chs <chs%NetBSD.org@localhost>
date:      Sun Mar 08 00:14:18 2020 +0000

description:
use a binary search in _kvm_pa2off().  this helps a lot for sparse dumps,
which can have millions of memory segments.

diffstat:

 lib/libkvm/kvm_x86_64.c |  65 ++++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 56 insertions(+), 9 deletions(-)

diffs (99 lines):

diff -r d960b20e1d55 -r 8b7b672f30fd lib/libkvm/kvm_x86_64.c
--- a/lib/libkvm/kvm_x86_64.c   Sun Mar 08 00:06:42 2020 +0000
+++ b/lib/libkvm/kvm_x86_64.c   Sun Mar 08 00:14:18 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kvm_x86_64.c,v 1.10 2014/02/19 20:21:22 dsl Exp $      */
+/*     $NetBSD: kvm_x86_64.c,v 1.11 2020/03/08 00:14:18 chs Exp $      */
 
 /*-
  * Copyright (c) 1989, 1992, 1993
@@ -38,7 +38,7 @@
 #if 0
 static char sccsid[] = "@(#)kvm_hp300.c        8.1 (Berkeley) 6/4/93";
 #else
-__RCSID("$NetBSD: kvm_x86_64.c,v 1.10 2014/02/19 20:21:22 dsl Exp $");
+__RCSID("$NetBSD: kvm_x86_64.c,v 1.11 2020/03/08 00:14:18 chs Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -186,6 +186,36 @@
        return (0);
 }
 
+struct p2o {
+       paddr_t pa;
+       psize_t sz;
+       off_t off;
+};
+
+static int
+cmp_p2o(const void *a, const void *b)
+{
+       const struct p2o *p1 = a;
+       const struct p2o *p2 = b;
+
+       /* If one range contains the start of the other, it's a match. */
+       if (p1->pa >= p2->pa && p1->pa < p2->pa + p2->sz) {
+               return 0;
+       }
+       if (p2->pa >= p1->pa && p2->pa < p1->pa + p1->sz) {
+               return 0;
+       }
+
+       /* Otherwise sort by pa. */
+       if (p1->pa < p2->pa)
+               return -1;
+       else if (p1->pa > p2->pa)
+               return 1;
+       else
+               return 0;
+}
+
+
 /*
  * Translate a physical address to a file-offset in the crash dump.
  */
@@ -197,19 +227,36 @@
        off_t off;
        int i;
 
+       static struct p2o *map;
+       struct p2o key, *val;
+
        cpu_kh = kd->cpu_data;
        ramsegs = (void *)((char *)(void *)cpu_kh + ALIGN(sizeof *cpu_kh));
 
-       off = 0;
-       for (i = 0; i < cpu_kh->nmemsegs; i++) {
-               if (pa >= ramsegs[i].start &&
-                   (pa - ramsegs[i].start) < ramsegs[i].size) {
-                       off += (pa - ramsegs[i].start);
-                       break;
+       if (map == NULL) {
+               map = calloc(sizeof *map, cpu_kh->nmemsegs);
+               off = 0;
+               for (i = 0; i < cpu_kh->nmemsegs; i++) {
+                       map[i].pa = ramsegs[i].start;
+                       map[i].sz = ramsegs[i].size;
+                       map[i].off = off;
+                       off += ramsegs[i].size;
                }
-               off += ramsegs[i].size;
+#if 0
+               /* The array appears to be sorted already */
+               qsort(map, cpu_kh->nmemsegs, sizeof(*map), cmp_p2o);
+#endif
        }
 
+       key.pa = pa;
+       key.sz = 1;
+       key.off = -1;
+       val = bsearch(&key, map, cpu_kh->nmemsegs, sizeof (key), cmp_p2o);
+       if (val)
+               off = val->off + pa - val->pa;
+       else
+               off = 0;
+
        return (kd->dump_off + off);
 }