Consider required constraint when moving pages from active to inactive lists.

Make sure low pages are deactivated first when there is a shortage of inactive
pages.  Without this the system can have a ton of high pages on the active list
and never swapout anything if there's a shortage of low pages.

This prevents a deadlock on amd64 reported and tested by bluhm@.

ok kettenis@

diff --git a/sys/uvm/uvm_pdaemon.c b/sys/uvm/uvm_pdaemon.c
index a403c30..9c3cc6c 100644 (file)
--- a/sys/uvm/uvm_pdaemon.c
+++ b/sys/uvm/uvm_pdaemon.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_pdaemon.c,v 1.106 2023/05/30 08:30:01 jsg Exp $   */
+/*     $OpenBSD: uvm_pdaemon.c,v 1.107 2023/10/16 11:32:54 mpi Exp $   */
 /*     $NetBSD: uvm_pdaemon.c,v 1.23 2000/08/20 10:24:14 bjh21 Exp $   */
 
 /*
@@ -102,8 +102,9 @@ extern void drmbackoff(long);
  */
 
 struct rwlock  *uvmpd_trylockowner(struct vm_page *);
-void           uvmpd_scan(struct uvm_pmalloc *);
-void           uvmpd_scan_inactive(struct uvm_pmalloc *, struct pglist *);
+void           uvmpd_scan(struct uvm_pmalloc *, struct uvm_constraint_range *);
+void           uvmpd_scan_inactive(struct uvm_pmalloc *,
+                   struct uvm_constraint_range *, struct pglist *);
 void           uvmpd_tune(void);
 void           uvmpd_drop(struct pglist *);
 void           uvmpd_dropswap(struct vm_page *);
@@ -283,7 +284,7 @@ uvm_pageout(void *arg)
                if (pma != NULL ||
                    ((uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) ||
                    ((uvmexp.inactive + BUFPAGES_INACT) < uvmexp.inactarg)) {
-                       uvmpd_scan(pma);
+                       uvmpd_scan(pma, &constraint);
                }
 
                /*
@@ -425,7 +426,8 @@ uvmpd_dropswap(struct vm_page *pg)
  * => we return TRUE if we are exiting because we met our target
  */
 void
-uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
+uvmpd_scan_inactive(struct uvm_pmalloc *pma,
+    struct uvm_constraint_range *constraint, struct pglist *pglst)
 {
        int free, result;
        struct vm_page *p, *nextpg;
@@ -440,6 +442,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
        boolean_t swap_backed;
        vaddr_t start;
        int dirtyreacts;
+       paddr_t paddr;
 
        /*
         * swslot is non-zero if we are building a swap cluster.  we want
@@ -451,22 +454,12 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
        dirtyreacts = 0;
        p = NULL;
 
-       /* Start with the first page on the list that fit in pma's ranges */
-       if (pma != NULL) {
-               paddr_t paddr;
-
-               TAILQ_FOREACH(p, pglst, pageq) {
-                       paddr = atop(VM_PAGE_TO_PHYS(p));
-                       if (paddr >= pma->pm_constraint.ucr_low &&
-                           paddr < pma->pm_constraint.ucr_high)
-                               break;
-               }
-
-       }
-
-       if (p == NULL) {
-               p = TAILQ_FIRST(pglst);
-               pma = NULL;
+       /* Start with the first page on the list that fit in `constraint' */
+       TAILQ_FOREACH(p, pglst, pageq) {
+               paddr = atop(VM_PAGE_TO_PHYS(p));
+               if (paddr >= constraint->ucr_low &&
+                   paddr < constraint->ucr_high)
+                       break;
        }
 
        for (; p != NULL || swslot != 0; p = nextpg) {
@@ -875,11 +868,12 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
  */
 
 void
-uvmpd_scan(struct uvm_pmalloc *pma)
+uvmpd_scan(struct uvm_pmalloc *pma, struct uvm_constraint_range *constraint)
 {
        int free, inactive_shortage, swap_shortage, pages_freed;
        struct vm_page *p, *nextpg;
        struct rwlock *slock;
+       paddr_t paddr;
 
        MUTEX_ASSERT_LOCKED(&uvm.pageqlock);
 
@@ -911,7 +905,7 @@ uvmpd_scan(struct uvm_pmalloc *pma)
         */
 
        pages_freed = uvmexp.pdfreed;
-       (void) uvmpd_scan_inactive(pma, &uvm.page_inactive);
+       (void) uvmpd_scan_inactive(pma, constraint, &uvm.page_inactive);
        pages_freed = uvmexp.pdfreed - pages_freed;
 
        /*
@@ -941,6 +935,14 @@ uvmpd_scan(struct uvm_pmalloc *pma)
                        continue;
                }
 
+               /*
+                * skip this page if it doesn't match the constraint.
+                */
+               paddr = atop(VM_PAGE_TO_PHYS(p));
+               if (paddr < constraint->ucr_low &&
+                   paddr >= constraint->ucr_high)
+                       continue;
+
                /*
                 * lock the page's owner.
                 */