MFC r290920:

Raise OOM when pagedaemon is unable to produce a free page in several
back-to-back passes.

2 files changed, 30 insertions, 14 deletions

diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index accf517..7ecb6c7 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -227,6 +227,7 @@ struct vm_domain {
 	long vmd_segs;	/* bitmask of the segments */
 	boolean_t vmd_oom;
 	int vmd_pass;	/* local pagedaemon pass */
+	int vmd_oom_seq;
 	int vmd_last_active_scan;
 	struct vm_page vmd_marker; /* marker for pagedaemon private use */
 };
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 871977f..156d11a 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -121,7 +121,8 @@ static void vm_pageout(void);
 static void vm_pageout_init(void);
 static int vm_pageout_clean(vm_page_t);
 static void vm_pageout_scan(struct vm_domain *vmd, int pass);
-static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass);
+static void vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
+    int starting_page_shortage);
 
 SYSINIT(pagedaemon_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, vm_pageout_init,
     NULL);
@@ -158,6 +159,7 @@ int vm_pages_needed;		/* Event on which pageout daemon sleeps */
 int vm_pageout_deficit;		/* Estimated number of pages deficit */
 int vm_pageout_pages_needed;	/* flag saying that the pageout daemon needs pages */
 int vm_pageout_wakeup_thresh;
+static int vm_pageout_oom_seq = 12;
 
 #if !defined(NO_SWAPPING)
 static int vm_pageout_req_swapout;	/* XXX */
@@ -217,6 +219,10 @@ static int pageout_lock_miss;
 SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss,
 	CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout");
 
+SYSCTL_INT(_vm, OID_AUTO, pageout_oom_seq,
+	CTLFLAG_RW, &vm_pageout_oom_seq, 0,
+	"back-to-back calls to oom detector to start OOM");
+
 #define VM_PAGEOUT_PAGE_COUNT 16
 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT;
 
@@ -941,7 +947,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 	long min_scan;
 	int act_delta, addl_page_shortage, deficit, maxscan, page_shortage;
 	int vnodes_skipped = 0;
-	int maxlaunder, scan_tick, scanned;
+	int maxlaunder, scan_tick, scanned, starting_page_shortage;
 	int lockmode;
 	boolean_t queues_locked;
 
@@ -981,6 +987,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 		page_shortage = vm_paging_target() + deficit;
 	} else
 		page_shortage = deficit = 0;
+	starting_page_shortage = page_shortage;
 
 	/*
 	 * maxlaunder limits the number of dirty pages we flush per scan.
@@ -1358,6 +1365,12 @@ relock_queues:
 		(void)speedup_syncer();
 
 	/*
+	 * If the inactive queue scan fails repeatedly to meet its
+	 * target, kill the largest process.
+	 */
+	vm_pageout_mightbe_oom(vmd, page_shortage, starting_page_shortage);
+
+	/*
 	 * Compute the number of pages we want to try to move from the
 	 * active queue to the inactive queue.
 	 */
@@ -1469,15 +1482,6 @@ relock_queues:
 		}
 	}
 #endif
-
-	/*
-	 * If we are critically low on one of RAM or swap and low on
-	 * the other, kill the largest process.  However, we avoid
-	 * doing this on the first pass in order to give ourselves a
-	 * chance to flush out dirty vnode-backed pages and to allow
-	 * active pages to be moved to the inactive queue and reclaimed.
-	 */
-	vm_pageout_mightbe_oom(vmd, pass);
 }
 
 static int vm_pageout_oom_vote;
@@ -1488,12 +1492,17 @@ static int vm_pageout_oom_vote;
  * failed to reach free target is premature.
  */
 static void
-vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
+vm_pageout_mightbe_oom(struct vm_domain *vmd, int page_shortage,
+    int starting_page_shortage)
 {
 	int old_vote;
 
-	if (pass <= 1 || !((swap_pager_avail < 64 && vm_page_count_min()) ||
-	    (swap_pager_full && vm_paging_target() > 0))) {
+	if (starting_page_shortage <= 0 || starting_page_shortage !=
+	    page_shortage)
+		vmd->vmd_oom_seq = 0;
+	else
+		vmd->vmd_oom_seq++;
+	if (vmd->vmd_oom_seq < vm_pageout_oom_seq) {
 		if (vmd->vmd_oom) {
 			vmd->vmd_oom = FALSE;
 			atomic_subtract_int(&vm_pageout_oom_vote, 1);
@@ -1501,6 +1510,12 @@ vm_pageout_mightbe_oom(struct vm_domain *vmd, int pass)
 		return;
 	}
 
+	/*
+	 * Do not follow the call sequence until OOM condition is
+	 * cleared.
+	 */
+	vmd->vmd_oom_seq = 0;
+
 	if (vmd->vmd_oom)
 		return;