Author: alc
Date: Tue Jul 16 03:09:03 2019
New Revision: 350021
URL: https://svnweb.freebsd.org/changeset/base/350021
Log:
Revert r349973. Upon further reflection, I realized that the comment
deleted by r349973 is still valid on i386. Restore it.
Discussed with: markj
Modified:
head/sys/i386/i386/pmap.c
Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c Mon Jul 15 23:43:38 2019 (r350020)
+++ head/sys/i386/i386/pmap.c Tue Jul 16 03:09:03 2019 (r350021)
@@ -5096,6 +5096,13 @@ __CONCAT(PMTYPE, ts_referenced)(vm_page_t m)
* reference bit will result in clearing that bit.
* This function is designed to avoid the selection of
* the same 4KB page for every 2- or 4MB page mapping.
+ *
+ * On demotion, a mapping that hasn't been referenced
+ * is simply destroyed. To avoid the possibility of a
+ * subsequent page fault on a demoted wired mapping,
+ * always leave its reference bit set. Moreover,
+ * since the superpage is wired, the current state of
+ * its reference bit won't affect page replacement.
*/
if ((((pa >> PAGE_SHIFT) ^ (pv->pv_va >> PDRSHIFT) ^
(uintptr_t)pmap) & (NPTEPG - 1)) == 0 &&
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