From 7f66ba575724cec7faaa95becba3805dc09a01dd Mon Sep 17 00:00:00 2001
From: Mark Johnston <mjohnston@isilon.com>
Date: Mon, 30 May 2016 12:22:27 -0700
Subject: [PATCH 2/4] Add a helper function for reading per-CPU vmmeter
 statistics.

Use it to read the pdwakeups value. In HEAD, this statistic is
maintained per-CPU.
---
 sys/sys/vmmeter.h   |  8 ++++++++
 sys/vm/vm_meter.c   | 34 +++++++++++++++++++++-------------
 sys/vm/vm_pageout.c | 10 ++++++----
 3 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/sys/sys/vmmeter.h b/sys/sys/vmmeter.h
index 9337aa3..eae9fce 100644
--- a/sys/sys/vmmeter.h
+++ b/sys/sys/vmmeter.h
@@ -197,6 +197,14 @@ vm_laundry_target(void)
 	    vm_paging_target());
 }
 
+/*
+ * Obtain the value of a per-CPU counter.
+ */
+#define	VM_METER_PCPU_CNT(member)					\
+	vm_meter_cnt(__offsetof(struct vmmeter, member))
+
+u_int	vm_meter_cnt(size_t);
+
 #endif
 
 /* systemwide totals computed every five seconds */
diff --git a/sys/vm/vm_meter.c b/sys/vm/vm_meter.c
index bb462d3..4bb079c 100644
--- a/sys/vm/vm_meter.c
+++ b/sys/vm/vm_meter.c
@@ -224,29 +224,37 @@ vmtotal(SYSCTL_HANDLER_ARGS)
 }
 
 /*
- * vcnt() -	accumulate statistics from all cpus and the global cnt
- *		structure.
+ * vm_meter_cnt() -	accumulate statistics from all cpus and the global cnt
+ *			structure.
  *
  *	The vmmeter structure is now per-cpu as well as global.  Those
  *	statistics which can be kept on a per-cpu basis (to avoid cache
  *	stalls between cpus) can be moved to the per-cpu vmmeter.  Remaining
  *	statistics, such as v_free_reserved, are left in the global
  *	structure.
- *
- * (sysctl_oid *oidp, void *arg1, int arg2, struct sysctl_req *req)
  */
-static int
-vcnt(SYSCTL_HANDLER_ARGS)
+u_int
+vm_meter_cnt(size_t offset)
 {
-	int count = *(int *)arg1;
-	int offset = (char *)arg1 - (char *)&vm_cnt;
+	struct pcpu *pcpu;
+	u_int count;
 	int i;
 
+	count = *(u_int *)((char *)&vm_cnt + offset);
 	CPU_FOREACH(i) {
-		struct pcpu *pcpu = pcpu_find(i);
-		count += *(int *)((char *)&pcpu->pc_cnt + offset);
+		pcpu = pcpu_find(i);
+		count += *(u_int *)((char *)&pcpu->pc_cnt + offset);
 	}
-	return (SYSCTL_OUT(req, &count, sizeof(int)));
+	return (count);
+}
+
+static int
+cnt_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	u_int count;
+
+	count = vm_meter_cnt((char *)arg1 - (char *)&vm_cnt);
+	return (SYSCTL_OUT(req, &count, sizeof(count)));
 }
 
 SYSCTL_PROC(_vm, VM_TOTAL, vmtotal, CTLTYPE_OPAQUE|CTLFLAG_RD|CTLFLAG_MPSAFE,
@@ -261,8 +269,8 @@ SYSCTL_NODE(_vm_stats, OID_AUTO, misc, CTLFLAG_RW, 0, "VM meter misc stats");
 
 #define	VM_STATS(parent, var, descr) \
 	SYSCTL_PROC(parent, OID_AUTO, var, \
-	    CTLTYPE_UINT | CTLFLAG_RD | CTLFLAG_MPSAFE, &vm_cnt.var, 0, vcnt, \
-	    "IU", descr)
+	    CTLTYPE_UINT | CTLFLAG_RD | CTLFLAG_MPSAFE, &vm_cnt.var, 0,	\
+	    cnt_sysctl, "IU", descr)
 #define	VM_STATS_VM(var, descr)		VM_STATS(_vm_stats_vm, var, descr)
 #define	VM_STATS_SYS(var, descr)	VM_STATS(_vm_stats_sys, var, descr)
 
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index ecb1f9e..0229ea2 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1110,7 +1110,8 @@ vm_pageout_laundry_worker(void *arg)
 {
 	struct vm_domain *domain;
 	uint64_t ninact, nlaundry;
-	int cycle, tcycle, domidx, gen, launder, laundered;
+	u_int wakeups, gen;
+	int cycle, tcycle, domidx, launder, laundered;
 	int shortfall, prev_shortfall, target;
 
 	domidx = (uintptr_t)arg;
@@ -1119,7 +1120,7 @@ vm_pageout_laundry_worker(void *arg)
 	vm_pageout_init_marker(&domain->vmd_laundry_marker, PQ_LAUNDRY);
 
 	cycle = tcycle = 0;
-	gen = -1;
+	gen = 0;
 	shortfall = prev_shortfall = 0;
 	target = 0;
 
@@ -1191,13 +1192,14 @@ vm_pageout_laundry_worker(void *arg)
 
 		ninact = vm_cnt.v_inactive_count;
 		nlaundry = vm_cnt.v_laundry_count;
+		wakeups = VM_METER_PCPU_CNT(v_pdwakeups);
 		if (ninact > 0 &&
-		    vm_cnt.v_pdwakeups != gen &&
+		    wakeups != gen &&
 		    vm_cnt.v_free_count < bkgrd_launder_thresh &&
 		    nlaundry * bkgrd_launder_ratio >= ninact) {
 			cycle = 0;
 			tcycle = VM_LAUNDER_INTERVAL;
-			gen = vm_cnt.v_pdwakeups;
+			gen = wakeups;
 			if (nlaundry >= ninact)
 				target = vm_cnt.v_free_target;
 			else
-- 
2.8.1