Do not consider adjacent pages when doing a CoW.

Those pages should already be entered, this speeds up CoW faults.

Stolen from NetBSD.

ok miod@, kettenis@

diff --git a/sys/uvm/uvm_fault.c b/sys/uvm/uvm_fault.c
index 56a30dc..ff4fb28 100644 (file)
--- a/sys/uvm/uvm_fault.c
+++ b/sys/uvm/uvm_fault.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_fault.c,v 1.129 2022/04/04 09:27:05 kettenis Exp $        */
+/*     $OpenBSD: uvm_fault.c,v 1.130 2022/06/28 10:38:55 mpi Exp $     */
 /*     $NetBSD: uvm_fault.c,v 1.51 2000/08/06 00:22:53 thorpej Exp $   */
 
 /*
@@ -736,6 +736,16 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
                return EFAULT;
        }
 
+       /*
+        * for a case 2B fault waste no time on adjacent pages because
+        * they are likely already entered.
+        */
+       if (uobj != NULL && amap != NULL &&
+           (flt->access_type & PROT_WRITE) != 0) {
+               /* wide fault (!narrow) */
+               flt->narrow = TRUE;
+       }
+
        /*
         * establish range of interest based on advice from mapper
         * and then clip to fit map entry.   note that we only want