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)
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