svn commit: r317061 - in head: libexec/rpc.rstatd sys/amd64/amd64 sys/amd64/include sys/arm/arm sys/arm/include sys/arm64/include sys/cddl/contrib/opensolaris/uts/common/fs/zfs sys/compat/linprocfs...

[Konstantin Belousov]

On Tue, May 02, 2017 at 11:31:21PM +1000, Bruce Evans wrote:
> On Tue, 2 May 2017, Konstantin Belousov wrote:
> > ENOMEM is, of course, the situation which I want to avoid.
> 
> Then you have to return no error, but truncate the value instead of
> clamping.  Anything else is incompatible.
I do not quite agree with the truncation part, bit I do not think that
it is too important. As I noted before, IMO the absolute numbers for
the counters have more values than per-interval diffs displayed by e.g.
systat. But if truncating causes less disagreement than clamping, lets
do truncation.

diff --git a/sys/vm/vm_meter.c b/sys/vm/vm_meter.c
index 5f4cd46ab1e..6266ef670a6 100644
--- a/sys/vm/vm_meter.c
+++ b/sys/vm/vm_meter.c
@@ -266,8 +266,27 @@ static SYSCTL_NODE(_vm_stats, OID_AUTO, vm, CTLFLAG_RW, 0,
 	"VM meter vm stats");
 SYSCTL_NODE(_vm_stats, OID_AUTO, misc, CTLFLAG_RW, 0, "VM meter misc stats");
 
+static int
+sysctl_handle_vmstat(SYSCTL_HANDLER_ARGS)
+{
+	uint64_t out;
+#ifdef COMPAT_FREEBSD11
+	uint32_t out32;
+#endif
+
+	out = counter_u64_fetch(*(counter_u64_t *)arg1);
+#ifdef COMPAT_FREEBSD11
+	if (req->oldlen == sizeof(out32)) {
+		out32 = (uint32_t)out; /* truncate */
+		return (SYSCTL_OUT(req, &out32, sizeof(out32)));
+	}
+#endif
+	return (SYSCTL_OUT(req, &out, sizeof(out)));
+}
+
 #define	VM_STATS(parent, var, descr) \
-    SYSCTL_COUNTER_U64(parent, OID_AUTO, var, CTLFLAG_RD, &vm_cnt.var, descr)
+    SYSCTL_OID(parent, OID_AUTO, var, CTLTYPE_U64 | CTLFLAG_MPSAFE | \
+    CTLFLAG_RD, &vm_cnt.var, 0, sysctl_handle_vmstat, "QU", 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)