[src/trunk]: src/sys/uvm uvm_fault_upper_lookup(): don't call pmap_extract() ...

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

details:   https://anonhg.NetBSD.org/src/rev/a8866f852cab
branches:  trunk
changeset: 746039:a8866f852cab
user:      ad <ad%NetBSD.org@localhost>
date:      Fri Mar 20 18:50:09 2020 +0000

description:
uvm_fault_upper_lookup(): don't call pmap_extract() and pmap_update() more
often than needed.

diffstat:

 sys/uvm/uvm_fault.c |  31 +++++++++++++++----------------
 1 files changed, 15 insertions(+), 16 deletions(-)

diffs (79 lines):

diff -r a2f6d832b1fd -r a8866f852cab sys/uvm/uvm_fault.c
--- a/sys/uvm/uvm_fault.c       Fri Mar 20 17:20:30 2020 +0000
+++ b/sys/uvm/uvm_fault.c       Fri Mar 20 18:50:09 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_fault.c,v 1.219 2020/03/17 18:31:39 ad Exp $       */
+/*     $NetBSD: uvm_fault.c,v 1.220 2020/03/20 18:50:09 ad Exp $       */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.219 2020/03/17 18:31:39 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.220 2020/03/20 18:50:09 ad Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -1166,6 +1166,7 @@
        int lcv;
        vaddr_t currva;
        bool shadowed __unused;
+       bool entered;
        UVMHIST_FUNC("uvm_fault_upper_lookup"); UVMHIST_CALLED(maphist);
 
        /* locked: maps(read), amap(if there) */
@@ -1179,18 +1180,9 @@
 
        currva = flt->startva;
        shadowed = false;
+       entered = false;
        for (lcv = 0; lcv < flt->npages; lcv++, currva += PAGE_SIZE) {
                /*
-                * don't play with VAs that are already mapped
-                * (except for center)
-                */
-               if (lcv != flt->centeridx &&
-                   pmap_extract(ufi->orig_map->pmap, currva, NULL)) {
-                       pages[lcv] = PGO_DONTCARE;
-                       continue;
-               }
-
-               /*
                 * unmapped or center page.   check if any anon at this level.
                 */
                if (amap == NULL || anons[lcv] == NULL) {
@@ -1213,12 +1205,21 @@
 
                KASSERT(anon->an_lock == amap->am_lock);
 
-               /* Ignore loaned and busy pages. */
-               if (pg && pg->loan_count == 0 && (pg->flags & PG_BUSY) == 0) {
+               /*
+                * ignore loaned and busy pages.
+                * don't play with VAs that are already mapped.
+                */
+
+               if (pg && pg->loan_count == 0 && (pg->flags & PG_BUSY) == 0 &&
+                   !pmap_extract(ufi->orig_map->pmap, currva, NULL)) {
                        uvm_fault_upper_neighbor(ufi, flt, currva,
                            pg, anon->an_ref > 1);
+                       entered = true;
                }
        }
+       if (entered) {
+               pmap_update(ufi->orig_map->pmap);
+       }
 
        /* locked: maps(read), amap(if there) */
        KASSERT(amap == NULL || rw_write_held(amap->am_lock));
@@ -1276,8 +1277,6 @@
            readonly ? (flt->enter_prot & ~VM_PROT_WRITE) :
            flt->enter_prot,
            PMAP_CANFAIL | (flt->wire_mapping ? PMAP_WIRED : 0));
-
-       pmap_update(ufi->orig_map->pmap);
 }
 
 /*