count how many times ifiqs enqueue and dequeue packets.

network cards try to enqueue a list of packets on an ifiq once per
interrupt and ifiqs already count how many packets they're handling.
this let's us see how well interrupt mitigation is working on a
ring or interface. ifiqs are supposed to provide backpressure
signalling to a driver if it enqueues a lot more work than it's
able to process in softnet, so recording dequeues let's us see this
ratio.

diff --git a/sys/net/ifq.c b/sys/net/ifq.c
index 26ac170..9977732 100644 (file)
--- a/sys/net/ifq.c
+++ b/sys/net/ifq.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ifq.c,v 1.46 2022/04/30 21:13:57 bluhm Exp $ */
+/*     $OpenBSD: ifq.c,v 1.47 2022/11/22 03:40:53 dlg Exp $ */
 
 /*
  * Copyright (c) 2015 David Gwynne <dlg@openbsd.org>
@@ -582,6 +582,9 @@ struct ifiq_kstat_data {
        struct kstat_kv kd_qdrops;
        struct kstat_kv kd_errors;
        struct kstat_kv kd_qlen;
+
+       struct kstat_kv kd_enqueues;
+       struct kstat_kv kd_dequeues;
 };
 
 static const struct ifiq_kstat_data ifiq_kstat_tpl = {
@@ -595,6 +598,11 @@ static const struct ifiq_kstat_data ifiq_kstat_tpl = {
            KSTAT_KV_T_COUNTER64, KSTAT_KV_U_PACKETS),
        KSTAT_KV_UNIT_INITIALIZER("qlen",
            KSTAT_KV_T_UINT32, KSTAT_KV_U_PACKETS),
+
+       KSTAT_KV_INITIALIZER("enqueues",
+           KSTAT_KV_T_COUNTER64),
+       KSTAT_KV_INITIALIZER("dequeues",
+           KSTAT_KV_T_COUNTER64),
 };
 
 int
@@ -610,6 +618,9 @@ ifiq_kstat_copy(struct kstat *ks, void *dst)
        kstat_kv_u64(&kd->kd_errors) = ifiq->ifiq_errors;
        kstat_kv_u32(&kd->kd_qlen) = ml_len(&ifiq->ifiq_ml);
 
+       kstat_kv_u64(&kd->kd_enqueues) = ifiq->ifiq_enqueues;
+       kstat_kv_u64(&kd->kd_dequeues) = ifiq->ifiq_dequeues;
+
        return (0);
 }
 #endif
@@ -721,8 +732,10 @@ ifiq_input(struct ifiqueue *ifiq, struct mbuf_list *ml)
        if (__predict_true(!ISSET(ifp->if_xflags, IFXF_MONITOR))) {
                if (len > ifiq_maxlen_drop)
                        ifiq->ifiq_qdrops += ml_len(ml);
-               else
+               else {
+                       ifiq->ifiq_enqueues++;
                        ml_enlist(&ifiq->ifiq_ml, ml);
+               }
        }
        mtx_leave(&ifiq->ifiq_mtx);
 
@@ -766,6 +779,7 @@ ifiq_process(void *arg)
                return;
 
        mtx_enter(&ifiq->ifiq_mtx);
+       ifiq->ifiq_dequeues++;
        ml = ifiq->ifiq_ml;
        ml_init(&ifiq->ifiq_ml);
        mtx_leave(&ifiq->ifiq_mtx);

diff --git a/sys/net/ifq.h b/sys/net/ifq.h
index 9764c9c..7818022 100644 (file)
--- a/sys/net/ifq.h
+++ b/sys/net/ifq.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ifq.h,v 1.34 2022/01/28 07:11:15 guenther Exp $ */
+/*     $OpenBSD: ifq.h,v 1.35 2022/11/22 03:40:53 dlg Exp $ */
 
 /*
  * Copyright (c) 2015 David Gwynne <dlg@openbsd.org>
@@ -95,6 +95,11 @@ struct ifiqueue {
        uint64_t                 ifiq_mcasts;
        uint64_t                 ifiq_noproto;
 
+       /* number of times a list of packets were put on ifiq_ml */
+       uint64_t                 ifiq_enqueues;
+       /* number of times a list of packets were pulled off ifiq_ml */
+       uint64_t                 ifiq_dequeues;
+
        struct kstat            *ifiq_kstat;
 
        /* properties */