[net-next-2.6 PATCH v4 1/2] net: implement mechanism for HW based QOS

[net-next-2.6 PATCH v4 1/2] net: implement mechanism for HW based QOS

[John Fastabend]

This patch provides a mechanism for lower layer devices to
steer traffic using skb->priority to tx queues. This allows
for hardware based QOS schemes to use the default qdisc without
incurring the penalties related to global state and the qdisc
lock. While reliably receiving skbs on the correct tx ring
to avoid head of line blocking resulting from shuffling in
the LLD. Finally, all the goodness from txq caching and xps/rps
can still be leveraged.

Many drivers and hardware exist with the ability to implement
QOS schemes in the hardware but currently these drivers tend
to rely on firmware to reroute specific traffic, a driver
specific select_queue or the queue_mapping action in the
qdisc.

By using select_queue for this drivers need to be updated for
each and every traffic type and we lose the goodness of much
of the upstream work. Firmware solutions are inherently
inflexible. And finally if admins are expected to build a
qdisc and filter rules to steer traffic this requires knowledge
of how the hardware is currently configured. The number of tx
queues and the queue offsets may change depending on resources.
Also this approach incurs all the overhead of a qdisc with filters.

With the mechanism in this patch users can set skb priority using
expected methods ie setsockopt() or the stack can set the priority
directly. Then the skb will be steered to the correct tx queues
aligned with hardware QOS traffic classes. In the normal case with
a single traffic class and all queues in this class everything
works as is until the LLD enables multiple tcs.

To steer the skb we mask out the lower 4 bits of the priority
and allow the hardware to configure upto 15 distinct classes
of traffic. This is expected to be sufficient for most applications
at any rate it is more then the 8021Q spec designates and is
equal to the number of prio bands currently implemented in
the default qdisc.

This in conjunction with a userspace application such as
lldpad can be used to implement 8021Q transmission selection
algorithms one of these algorithms being the extended transmission
selection algorithm currently being used for DCB.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
---

 include/linux/netdevice.h |   62 +++++++++++++++++++++++++++++++++++++++++++++
 net/core/dev.c            |   10 +++++++
 2 files changed, 71 insertions(+), 1 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cc916c5..073c48d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -646,6 +646,14 @@ struct xps_dev_maps {
     (nr_cpu_ids * sizeof(struct xps_map *)))
 #endif /* CONFIG_XPS */
 
+#define TC_MAX_QUEUE	16
+#define TC_BITMASK	15
+/* HW offloaded queuing disciplines txq count and offset maps */
+struct netdev_tc_txq {
+	u16 count;
+	u16 offset;
+};
+
 /*
  * This structure defines the management hooks for network devices.
  * The following hooks can be defined; unless noted otherwise, they are
@@ -1146,6 +1154,9 @@ struct net_device {
 	/* Data Center Bridging netlink ops */
 	const struct dcbnl_rtnl_ops *dcbnl_ops;
 #endif
+	u8 num_tc;
+	struct netdev_tc_txq tc_to_txq[TC_MAX_QUEUE];
+	u8 prio_tc_map[TC_BITMASK+1];
 
 #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
 	/* max exchange id for FCoE LRO by ddp */
@@ -1162,6 +1173,57 @@ struct net_device {
 #define	NETDEV_ALIGN		32
 
 static inline
+int netdev_get_prio_tc_map(const struct net_device *dev, u32 prio)
+{
+	return dev->prio_tc_map[prio & TC_BITMASK];
+}
+
+static inline
+int netdev_set_prio_tc_map(struct net_device *dev, u8 prio, u8 tc)
+{
+	if (tc >= dev->num_tc)
+		return -EINVAL;
+
+	dev->prio_tc_map[prio & TC_BITMASK] = tc & TC_BITMASK;
+	return 0;
+}
+
+static inline
+void netdev_reset_tc(struct net_device *dev)
+{
+	dev->num_tc = 0;
+	memset(dev->tc_to_txq, 0, sizeof(dev->tc_to_txq));
+	memset(dev->prio_tc_map, 0, sizeof(dev->prio_tc_map));
+}
+
+static inline
+int netdev_set_tc_queue(struct net_device *dev, u8 tc, u16 count, u16 offset)
+{
+	if (tc >= dev->num_tc)
+		return -EINVAL;
+
+	dev->tc_to_txq[tc].count = count;
+	dev->tc_to_txq[tc].offset = offset;
+	return 0;
+}
+
+static inline
+int netdev_set_num_tc(struct net_device *dev, u8 num_tc)
+{
+	if (num_tc > TC_MAX_QUEUE)
+		return -EINVAL;
+
+	dev->num_tc = num_tc;
+	return 0;
+}
+
+static inline
+u8 netdev_get_num_tc(const struct net_device *dev)
+{
+	return dev->num_tc;
+}
+
+static inline
 struct netdev_queue *netdev_get_tx_queue(const struct net_device *dev,
 					 unsigned int index)
 {
diff --git a/net/core/dev.c b/net/core/dev.c
index a215269..38318e2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2165,6 +2165,8 @@ u16 __skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb,
 		  unsigned int num_tx_queues)
 {
 	u32 hash;
+	u16 qoffset = 0;
+	u16 qcount = num_tx_queues;
 
 	if (skb_rx_queue_recorded(skb)) {
 		hash = skb_get_rx_queue(skb);
@@ -2173,13 +2175,19 @@ u16 __skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb,
 		return hash;
 	}
 
+	if (dev->num_tc) {
+		u8 tc = netdev_get_prio_tc_map(dev, skb->priority);
+		qoffset = dev->tc_to_txq[tc].offset;
+		qcount = dev->tc_to_txq[tc].count;
+	}
+
 	if (skb->sk && skb->sk->sk_hash)
 		hash = skb->sk->sk_hash;
 	else
 		hash = (__force u16) skb->protocol ^ skb->rxhash;
 	hash = jhash_1word(hash, hashrnd);
 
-	return (u16) (((u64) hash * num_tx_queues) >> 32);
+	return (u16) (((u64) hash * qcount) >> 32) + qoffset;
 }
 EXPORT_SYMBOL(__skb_tx_hash);
 

[net-next-2.6 PATCH v4 2/2] net_sched: implement a root container qdisc sch_mclass

[John Fastabend]

This implements a mqprio queueing discipline that by default creates
a pfifo_fast qdisc per tx queue and provides the needed configuration
interface.

Using the mqprio qdisc the number of tcs currently in use along
with the range of queues alloted to each class can be configured. By
default skbs are mapped to traffic classes using the skb priority.
This mapping is configurable.

Configurable parameters,

struct tc_mclass_qopt {
        __u8    num_tc;
        __u8    prio_tc_map[16];
        __u8    hw;
        __u16   count[16];
        __u16   offset[16];
};

Here the count/offset pairing give the queue alignment and the
prio_tc_map gives the mapping from skb->priority to tc.

The hw bit determines if the hardware should configure the count
and offset values. If the hardware bit is set then the operation
will fail if the hardware does not implement the ndo_setup_tc
operation. This is to avoid undetermined states where the hardware
may or may not control the queue mapping. Also minimal bounds
checking is done on the count/offset to verify a queue does not
exceed num_tx_queues and that queue ranges do not overlap. Otherwise
it is left to user policy or hardware configuration to create
useful mappings.

It is expected that hardware QOS schemes can be implemented by
creating appropriate mappings of queues in ndo_tc_setup().

One expected use case is drivers will use the ndo_setup_tc to map
queue ranges onto 802.1Q traffic classes. This provides a generic
mechanism to map network traffic onto these traffic classes and
removes the need for lower layer drivers to no specifics about
traffic types.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
---

 include/linux/netdevice.h |    3 
 include/linux/pkt_sched.h |    9 +
 net/sched/Kconfig         |   10 +
 net/sched/Makefile        |    1 
 net/sched/sch_generic.c   |    4 +
 net/sched/sch_mqprio.c    |  357 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 384 insertions(+), 0 deletions(-)
 create mode 100644 net/sched/sch_mqprio.c

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 073c48d..f90a863 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -764,6 +764,8 @@ struct netdev_tc_txq {
  * int (*ndo_set_vf_port)(struct net_device *dev, int vf,
  *			  struct nlattr *port[]);
  * int (*ndo_get_vf_port)(struct net_device *dev, int vf, struct sk_buff *skb);
+ *
+ * int (*ndo_setup_tc)(struct net_device *dev, int tc);
  */
 #define HAVE_NET_DEVICE_OPS
 struct net_device_ops {
@@ -822,6 +824,7 @@ struct net_device_ops {
 						   struct nlattr *port[]);
 	int			(*ndo_get_vf_port)(struct net_device *dev,
 						   int vf, struct sk_buff *skb);
+	int			(*ndo_setup_tc)(struct net_device *dev, u8 tc);
 #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
 	int			(*ndo_fcoe_enable)(struct net_device *dev);
 	int			(*ndo_fcoe_disable)(struct net_device *dev);
diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 2cfa4bc..8e29fa6 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -481,4 +481,13 @@ struct tc_drr_stats {
 	__u32	deficit;
 };
 
+/* MCLASS */
+struct tc_mqprio_qopt {
+	__u8	num_tc;
+	__u8	prio_tc_map[16];
+	__u8	hw;
+	__u16	count[16];
+	__u16	offset[16];
+};
+
 #endif
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a36270a..e42853b 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -205,6 +205,16 @@ config NET_SCH_DRR
 
 	  If unsure, say N.
 
+config NET_SCH_MQPRIO
+	tristate "Multi-queue priority scheduler (MQPRIO)"
+	help
+	  Say Y here if you want to use the Multi-queue Priority scheduler.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called sch_mqprio.
+
+	  If unsure, say N.
+
 config NET_SCH_INGRESS
 	tristate "Ingress Qdisc"
 	depends on NET_CLS_ACT
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 960f5db..26ce681 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_NET_SCH_MULTIQ)	+= sch_multiq.o
 obj-$(CONFIG_NET_SCH_ATM)	+= sch_atm.o
 obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o
 obj-$(CONFIG_NET_SCH_DRR)	+= sch_drr.o
+obj-$(CONFIG_NET_SCH_MQPRIO)	+= sch_mqprio.o
 obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o
 obj-$(CONFIG_NET_CLS_FW)	+= cls_fw.o
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 34dc598..723b278 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -540,6 +540,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
 	.dump		=	pfifo_fast_dump,
 	.owner		=	THIS_MODULE,
 };
+EXPORT_SYMBOL(pfifo_fast_ops);
 
 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 			  struct Qdisc_ops *ops)
@@ -674,6 +675,7 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
 
 	return oqdisc;
 }
+EXPORT_SYMBOL(dev_graft_qdisc);
 
 static void attach_one_default_qdisc(struct net_device *dev,
 				     struct netdev_queue *dev_queue,
@@ -761,6 +763,7 @@ void dev_activate(struct net_device *dev)
 		dev_watchdog_up(dev);
 	}
 }
+EXPORT_SYMBOL(dev_activate);
 
 static void dev_deactivate_queue(struct net_device *dev,
 				 struct netdev_queue *dev_queue,
@@ -840,6 +843,7 @@ void dev_deactivate(struct net_device *dev)
 	list_add(&dev->unreg_list, &single);
 	dev_deactivate_many(&single);
 }
+EXPORT_SYMBOL(dev_deactivate);
 
 static void dev_init_scheduler_queue(struct net_device *dev,
 				     struct netdev_queue *dev_queue,
diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
new file mode 100644
index 0000000..e9e74c7
--- /dev/null
+++ b/net/sched/sch_mqprio.c
@@ -0,0 +1,357 @@
+/*
+ * net/sched/sch_mqprio.c
+ *
+ * Copyright (c) 2010 John Fastabend <john.r.fastabend@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/sch_generic.h>
+
+struct mqprio_sched {
+	struct Qdisc		**qdiscs;
+	int hw_owned;
+};
+
+static void mqprio_destroy(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mqprio_sched *priv = qdisc_priv(sch);
+	unsigned int ntx;
+
+	if (!priv->qdiscs)
+		return;
+
+	for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
+		qdisc_destroy(priv->qdiscs[ntx]);
+
+	if (priv->hw_owned && dev->netdev_ops->ndo_setup_tc)
+		dev->netdev_ops->ndo_setup_tc(dev, 0);
+	else
+		netdev_set_num_tc(dev, 0);
+
+	kfree(priv->qdiscs);
+}
+
+static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
+{
+	int i, j;
+
+	/* Verify num_tc is not out of max range */
+	if (qopt->num_tc > TC_MAX_QUEUE)
+		return -EINVAL;
+
+	for (i = 0; i < qopt->num_tc; i++) {
+		unsigned int last = qopt->offset[i] + qopt->count[i];
+		/* Verify the queue offset is in the num tx range */
+		if (qopt->offset[i] >= dev->num_tx_queues)
+			return -EINVAL;
+		/* Verify the queue count is in tx range being equal to the
+		 * num_tx_queues indicates the last queue is in use.
+		 */
+		else if (last > dev->num_tx_queues)
+			return -EINVAL;
+
+		/* Verify that the offset and counts do not overlap */
+		for (j = i + 1; j < qopt->num_tc; j++) {
+			if (last > qopt->offset[j])
+				return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int mqprio_init(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mqprio_sched *priv = qdisc_priv(sch);
+	struct netdev_queue *dev_queue;
+	struct Qdisc *qdisc;
+	int i, err = -EOPNOTSUPP;
+	struct tc_mqprio_qopt *qopt = NULL;
+
+	/* Unwind attributes on failure */
+	u8 unwnd_tc = dev->num_tc;
+	u8 unwnd_map[TC_BITMASK+1];
+	struct netdev_tc_txq unwnd_txq[TC_MAX_QUEUE];
+
+	if (sch->parent != TC_H_ROOT)
+		return -EOPNOTSUPP;
+
+	if (!netif_is_multiqueue(dev))
+		return -EOPNOTSUPP;
+
+	if (nla_len(opt) < sizeof(*qopt))
+		return -EINVAL;
+	qopt = nla_data(opt);
+
+	memcpy(unwnd_map, dev->prio_tc_map, sizeof(unwnd_map));
+	memcpy(unwnd_txq, dev->tc_to_txq, sizeof(unwnd_txq));
+
+	/* If the mqprio options indicate that hardware should own
+	 * the queue mapping then run ndo_setup_tc if this can not
+	 * be done fail immediately.
+	 */
+	if (qopt->hw && dev->netdev_ops->ndo_setup_tc) {
+		priv->hw_owned = 1;
+		err = dev->netdev_ops->ndo_setup_tc(dev, qopt->num_tc);
+		if (err)
+			return err;
+	} else if (!qopt->hw) {
+		if (mqprio_parse_opt(dev, qopt))
+			return -EINVAL;
+
+		if (netdev_set_num_tc(dev, qopt->num_tc))
+			return -EINVAL;
+
+		for (i = 0; i < qopt->num_tc; i++)
+			netdev_set_tc_queue(dev, i,
+					    qopt->count[i], qopt->offset[i]);
+	} else {
+		return -EINVAL;
+	}
+
+	/* Always use supplied priority mappings */
+	for (i = 0; i < TC_BITMASK+1; i++) {
+		if (netdev_set_prio_tc_map(dev, i, qopt->prio_tc_map[i])) {
+			err = -EINVAL;
+			goto tc_err;
+		}
+	}
+
+	/* pre-allocate qdisc, attachment can't fail */
+	priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
+			       GFP_KERNEL);
+	if (priv->qdiscs == NULL) {
+		err = -ENOMEM;
+		goto tc_err;
+	}
+
+	for (i = 0; i < dev->num_tx_queues; i++) {
+		dev_queue = netdev_get_tx_queue(dev, i);
+		qdisc = qdisc_create_dflt(dev_queue, &pfifo_fast_ops,
+					  TC_H_MAKE(TC_H_MAJ(sch->handle),
+						    TC_H_MIN(i + 1)));
+		if (qdisc == NULL) {
+			err = -ENOMEM;
+			goto err;
+		}
+		qdisc->flags |= TCQ_F_CAN_BYPASS;
+		priv->qdiscs[i] = qdisc;
+	}
+
+	sch->flags |= TCQ_F_MQROOT;
+	return 0;
+
+err:
+	mqprio_destroy(sch);
+tc_err:
+	if (priv->hw_owned)
+		dev->netdev_ops->ndo_setup_tc(dev, unwnd_tc);
+	else
+		netdev_set_num_tc(dev, unwnd_tc);
+
+	memcpy(dev->prio_tc_map, unwnd_map, sizeof(unwnd_map));
+	memcpy(dev->tc_to_txq, unwnd_txq, sizeof(unwnd_txq));
+
+	return err;
+}
+
+static void mqprio_attach(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mqprio_sched *priv = qdisc_priv(sch);
+	struct Qdisc *qdisc;
+	unsigned int ntx;
+
+	/* Attach underlying qdisc */
+	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
+		qdisc = priv->qdiscs[ntx];
+		qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
+		if (qdisc)
+			qdisc_destroy(qdisc);
+	}
+	kfree(priv->qdiscs);
+	priv->qdiscs = NULL;
+}
+
+static struct netdev_queue *mqprio_queue_get(struct Qdisc *sch,
+					     unsigned long cl)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	unsigned long ntx = cl - 1;
+
+	if (ntx >= dev->num_tx_queues)
+		return NULL;
+	return netdev_get_tx_queue(dev, ntx);
+}
+
+static int mqprio_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
+		    struct Qdisc **old)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
+
+	if (dev->flags & IFF_UP)
+		dev_deactivate(dev);
+
+	*old = dev_graft_qdisc(dev_queue, new);
+
+	if (dev->flags & IFF_UP)
+		dev_activate(dev);
+
+	return 0;
+}
+
+static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct mqprio_sched *priv = qdisc_priv(sch);
+	unsigned char *b = skb_tail_pointer(skb);
+	struct tc_mqprio_qopt opt;
+	struct Qdisc *qdisc;
+	unsigned int i;
+
+	sch->q.qlen = 0;
+	memset(&sch->bstats, 0, sizeof(sch->bstats));
+	memset(&sch->qstats, 0, sizeof(sch->qstats));
+
+	for (i = 0; i < dev->num_tx_queues; i++) {
+		qdisc = netdev_get_tx_queue(dev, i)->qdisc;
+		spin_lock_bh(qdisc_lock(qdisc));
+		sch->q.qlen		+= qdisc->q.qlen;
+		sch->bstats.bytes	+= qdisc->bstats.bytes;
+		sch->bstats.packets	+= qdisc->bstats.packets;
+		sch->qstats.qlen	+= qdisc->qstats.qlen;
+		sch->qstats.backlog	+= qdisc->qstats.backlog;
+		sch->qstats.drops	+= qdisc->qstats.drops;
+		sch->qstats.requeues	+= qdisc->qstats.requeues;
+		sch->qstats.overlimits	+= qdisc->qstats.overlimits;
+		spin_unlock_bh(qdisc_lock(qdisc));
+	}
+
+	opt.num_tc = dev->num_tc;
+	memcpy(opt.prio_tc_map, dev->prio_tc_map, 16);
+	opt.hw = priv->hw_owned;
+
+	for (i = 0; i < dev->num_tc; i++) {
+		opt.count[i] = dev->tc_to_txq[i].count;
+		opt.offset[i] = dev->tc_to_txq[i].offset;
+	}
+
+	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
+
+	return skb->len;
+nla_put_failure:
+	nlmsg_trim(skb, b);
+	return -1;
+}
+
+static struct Qdisc *mqprio_leaf(struct Qdisc *sch, unsigned long cl)
+{
+	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
+
+	return dev_queue->qdisc_sleeping;
+}
+
+static unsigned long mqprio_get(struct Qdisc *sch, u32 classid)
+{
+	unsigned int ntx = TC_H_MIN(classid);
+
+	if (!mqprio_queue_get(sch, ntx))
+		return 0;
+	return ntx;
+}
+
+static void mqprio_put(struct Qdisc *sch, unsigned long cl)
+{
+}
+
+static int mqprio_dump_class(struct Qdisc *sch, unsigned long cl,
+			 struct sk_buff *skb, struct tcmsg *tcm)
+{
+	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
+
+	tcm->tcm_parent = TC_H_ROOT;
+	tcm->tcm_handle |= TC_H_MIN(cl);
+	tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
+	return 0;
+}
+
+static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
+			       struct gnet_dump *d)
+{
+	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
+
+	sch = dev_queue->qdisc_sleeping;
+	sch->qstats.qlen = sch->q.qlen;
+	if (gnet_stats_copy_basic(d, &sch->bstats) < 0 ||
+	    gnet_stats_copy_queue(d, &sch->qstats) < 0)
+		return -1;
+	return 0;
+}
+
+static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	unsigned long ntx;
+
+	if (arg->stop)
+		return;
+
+	arg->count = arg->skip;
+	for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
+		if (arg->fn(sch, ntx + 1, arg) < 0) {
+			arg->stop = 1;
+			break;
+		}
+		arg->count++;
+	}
+}
+
+static const struct Qdisc_class_ops mqprio_class_ops = {
+	.graft		= mqprio_graft,
+	.leaf		= mqprio_leaf,
+	.get		= mqprio_get,
+	.put		= mqprio_put,
+	.walk		= mqprio_walk,
+	.dump		= mqprio_dump_class,
+	.dump_stats	= mqprio_dump_class_stats,
+};
+
+struct Qdisc_ops mqprio_qdisc_ops __read_mostly = {
+	.cl_ops		= &mqprio_class_ops,
+	.id		= "mqprio",
+	.priv_size	= sizeof(struct mqprio_sched),
+	.init		= mqprio_init,
+	.destroy	= mqprio_destroy,
+	.attach		= mqprio_attach,
+	.dump		= mqprio_dump,
+	.owner		= THIS_MODULE,
+};
+
+static int __init mqprio_module_init(void)
+{
+	return register_qdisc(&mqprio_qdisc_ops);
+}
+
+static void __exit mqprio_module_exit(void)
+{
+	unregister_qdisc(&mqprio_qdisc_ops);
+}
+
+module_init(mqprio_module_init);
+module_exit(mqprio_module_exit);
+
+MODULE_LICENSE("GPL");

Re: [net-next-2.6 PATCH v4 2/2] net_sched: implement a root container qdisc sch_mclass

[Eric Dumazet]

Le lundi 03 janvier 2011 à 19:05 -0800, John Fastabend a écrit :
> This implements a mqprio queueing discipline that by default creates
> a pfifo_fast qdisc per tx queue and provides the needed configuration
> interface.


> +static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	unsigned char *b = skb_tail_pointer(skb);
> +	struct tc_mqprio_qopt opt;
> +	struct Qdisc *qdisc;
> +	unsigned int i;
> +
> +	sch->q.qlen = 0;
> +	memset(&sch->bstats, 0, sizeof(sch->bstats));
> +	memset(&sch->qstats, 0, sizeof(sch->qstats));
> +
> +	for (i = 0; i < dev->num_tx_queues; i++) {
> +		qdisc = netdev_get_tx_queue(dev, i)->qdisc;
> +		spin_lock_bh(qdisc_lock(qdisc));
> +		sch->q.qlen		+= qdisc->q.qlen;
> +		sch->bstats.bytes	+= qdisc->bstats.bytes;
> +		sch->bstats.packets	+= qdisc->bstats.packets;
> +		sch->qstats.qlen	+= qdisc->qstats.qlen;
> +		sch->qstats.backlog	+= qdisc->qstats.backlog;
> +		sch->qstats.drops	+= qdisc->qstats.drops;
> +		sch->qstats.requeues	+= qdisc->qstats.requeues;
> +		sch->qstats.overlimits	+= qdisc->qstats.overlimits;
> +		spin_unlock_bh(qdisc_lock(qdisc));
> +	}
> +

I understand this code already exists in mq, I just want to note that
some qdiscs update their stats in their dump() subroutine, because their
enqueue()/dequeue() doesnt update all fields.

We might add a gather_stats() method, eventually, to get rid of all
oddities we currently have with 0 backlogs (or qlen) here and here ;)

For example, I am not even sure qdisc->qstats.qlen should not be
replaced by to qdisc->qstats.qlen in your loop, as done in
mqprio_dump_class_stats()

Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>

Re: [net-next-2.6 PATCH v4 2/2] net_sched: implement a root container qdisc sch_mclass

[Jarek Poplawski]

On Mon, Jan 03, 2011 at 07:05:58PM -0800, John Fastabend wrote:
> This implements a mqprio queueing discipline that by default creates
> a pfifo_fast qdisc per tx queue and provides the needed configuration
> interface.
> 
> Using the mqprio qdisc the number of tcs currently in use along
> with the range of queues alloted to each class can be configured. By
> default skbs are mapped to traffic classes using the skb priority.
> This mapping is configurable.
> 
> Configurable parameters,
> 
> struct tc_mclass_qopt {

Now *_mqprio here and in the subject of the message.

>         __u8    num_tc;
>         __u8    prio_tc_map[16];

s/16/TC_SOMETHING/

>         __u8    hw;
>         __u16   count[16];
>         __u16   offset[16];
> };
> 
> Here the count/offset pairing give the queue alignment and the
> prio_tc_map gives the mapping from skb->priority to tc.
> 
> The hw bit determines if the hardware should configure the count
> and offset values. If the hardware bit is set then the operation
> will fail if the hardware does not implement the ndo_setup_tc
> operation. This is to avoid undetermined states where the hardware
> may or may not control the queue mapping. Also minimal bounds
> checking is done on the count/offset to verify a queue does not
> exceed num_tx_queues and that queue ranges do not overlap. Otherwise
> it is left to user policy or hardware configuration to create
> useful mappings.
> 
> It is expected that hardware QOS schemes can be implemented by
> creating appropriate mappings of queues in ndo_tc_setup().
> 
> One expected use case is drivers will use the ndo_setup_tc to map
> queue ranges onto 802.1Q traffic classes. This provides a generic
> mechanism to map network traffic onto these traffic classes and
> removes the need for lower layer drivers to no specifics about
> traffic types.
> 
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> ---
> 
>  include/linux/netdevice.h |    3 
>  include/linux/pkt_sched.h |    9 +
>  net/sched/Kconfig         |   10 +
>  net/sched/Makefile        |    1 
>  net/sched/sch_generic.c   |    4 +
>  net/sched/sch_mqprio.c    |  357 +++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 384 insertions(+), 0 deletions(-)
>  create mode 100644 net/sched/sch_mqprio.c
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 073c48d..f90a863 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -764,6 +764,8 @@ struct netdev_tc_txq {
>   * int (*ndo_set_vf_port)(struct net_device *dev, int vf,
>   *			  struct nlattr *port[]);
>   * int (*ndo_get_vf_port)(struct net_device *dev, int vf, struct sk_buff *skb);
> + *
> + * int (*ndo_setup_tc)(struct net_device *dev, int tc);
>   */
>  #define HAVE_NET_DEVICE_OPS
>  struct net_device_ops {
> @@ -822,6 +824,7 @@ struct net_device_ops {
>  						   struct nlattr *port[]);
>  	int			(*ndo_get_vf_port)(struct net_device *dev,
>  						   int vf, struct sk_buff *skb);
> +	int			(*ndo_setup_tc)(struct net_device *dev, u8 tc);
>  #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
>  	int			(*ndo_fcoe_enable)(struct net_device *dev);
>  	int			(*ndo_fcoe_disable)(struct net_device *dev);
> diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
> index 2cfa4bc..8e29fa6 100644
> --- a/include/linux/pkt_sched.h
> +++ b/include/linux/pkt_sched.h
> @@ -481,4 +481,13 @@ struct tc_drr_stats {
>  	__u32	deficit;
>  };
>  
> +/* MCLASS */

/* MQPRIO */

> +struct tc_mqprio_qopt {
> +	__u8	num_tc;
> +	__u8	prio_tc_map[16];
> +	__u8	hw;
> +	__u16	count[16];
> +	__u16	offset[16];

s/16/TC_SOMETHING/

> +};
> +
>  #endif
> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
> index a36270a..e42853b 100644
> --- a/net/sched/Kconfig
> +++ b/net/sched/Kconfig
> @@ -205,6 +205,16 @@ config NET_SCH_DRR
>  
>  	  If unsure, say N.
>  
> +config NET_SCH_MQPRIO
> +	tristate "Multi-queue priority scheduler (MQPRIO)"
> +	help
> +	  Say Y here if you want to use the Multi-queue Priority scheduler.

We might mention about a proper NIC required.

> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called sch_mqprio.
> +
> +	  If unsure, say N.
> +
>  config NET_SCH_INGRESS
>  	tristate "Ingress Qdisc"
>  	depends on NET_CLS_ACT
> diff --git a/net/sched/Makefile b/net/sched/Makefile
> index 960f5db..26ce681 100644
> --- a/net/sched/Makefile
> +++ b/net/sched/Makefile
> @@ -32,6 +32,7 @@ obj-$(CONFIG_NET_SCH_MULTIQ)	+= sch_multiq.o
>  obj-$(CONFIG_NET_SCH_ATM)	+= sch_atm.o
>  obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o
>  obj-$(CONFIG_NET_SCH_DRR)	+= sch_drr.o
> +obj-$(CONFIG_NET_SCH_MQPRIO)	+= sch_mqprio.o
>  obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
>  obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o
>  obj-$(CONFIG_NET_CLS_FW)	+= cls_fw.o
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 34dc598..723b278 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -540,6 +540,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
>  	.dump		=	pfifo_fast_dump,
>  	.owner		=	THIS_MODULE,
>  };
> +EXPORT_SYMBOL(pfifo_fast_ops);
>  
>  struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
>  			  struct Qdisc_ops *ops)
> @@ -674,6 +675,7 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
>  
>  	return oqdisc;
>  }
> +EXPORT_SYMBOL(dev_graft_qdisc);
>  
>  static void attach_one_default_qdisc(struct net_device *dev,
>  				     struct netdev_queue *dev_queue,
> @@ -761,6 +763,7 @@ void dev_activate(struct net_device *dev)
>  		dev_watchdog_up(dev);
>  	}
>  }
> +EXPORT_SYMBOL(dev_activate);
>  
>  static void dev_deactivate_queue(struct net_device *dev,
>  				 struct netdev_queue *dev_queue,
> @@ -840,6 +843,7 @@ void dev_deactivate(struct net_device *dev)
>  	list_add(&dev->unreg_list, &single);
>  	dev_deactivate_many(&single);
>  }
> +EXPORT_SYMBOL(dev_deactivate);
>  
>  static void dev_init_scheduler_queue(struct net_device *dev,
>  				     struct netdev_queue *dev_queue,
> diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
> new file mode 100644
> index 0000000..e9e74c7
> --- /dev/null
> +++ b/net/sched/sch_mqprio.c
> @@ -0,0 +1,357 @@
> +/*
> + * net/sched/sch_mqprio.c
> + *
> + * Copyright (c) 2010 John Fastabend <john.r.fastabend@intel.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + */
> +
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/kernel.h>
> +#include <linux/string.h>
> +#include <linux/errno.h>
> +#include <linux/skbuff.h>
> +#include <net/netlink.h>
> +#include <net/pkt_sched.h>
> +#include <net/sch_generic.h>
> +
> +struct mqprio_sched {
> +	struct Qdisc		**qdiscs;
> +	int hw_owned;
> +};
> +
> +static void mqprio_destroy(struct Qdisc *sch)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	unsigned int ntx;
> +
> +	if (!priv->qdiscs)
> +		return;
> +
> +	for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
> +		qdisc_destroy(priv->qdiscs[ntx]);
> +
> +	if (priv->hw_owned && dev->netdev_ops->ndo_setup_tc)
> +		dev->netdev_ops->ndo_setup_tc(dev, 0);
> +	else
> +		netdev_set_num_tc(dev, 0);

I'm not sure why this unsetting is needed in case it was set by a
driver before mqprio was created.

> +
> +	kfree(priv->qdiscs);
> +}
> +
> +static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
> +{
> +	int i, j;
> +
> +	/* Verify num_tc is not out of max range */
> +	if (qopt->num_tc > TC_MAX_QUEUE)
> +		return -EINVAL;
> +
> +	for (i = 0; i < qopt->num_tc; i++) {
> +		unsigned int last = qopt->offset[i] + qopt->count[i];
> +		/* Verify the queue offset is in the num tx range */
> +		if (qopt->offset[i] >= dev->num_tx_queues)
> +			return -EINVAL;
> +		/* Verify the queue count is in tx range being equal to the
> +		 * num_tx_queues indicates the last queue is in use.
> +		 */
> +		else if (last > dev->num_tx_queues)
> +			return -EINVAL;
> +
> +		/* Verify that the offset and counts do not overlap */
> +		for (j = i + 1; j < qopt->num_tc; j++) {
> +			if (last > qopt->offset[j])
> +				return -EINVAL;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int mqprio_init(struct Qdisc *sch, struct nlattr *opt)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	struct netdev_queue *dev_queue;
> +	struct Qdisc *qdisc;
> +	int i, err = -EOPNOTSUPP;
> +	struct tc_mqprio_qopt *qopt = NULL;
> +
> +	/* Unwind attributes on failure */
> +	u8 unwnd_tc = dev->num_tc;
> +	u8 unwnd_map[TC_BITMASK+1];

 	u8 unwnd_map[TC_BITMASK + 1];

> +	struct netdev_tc_txq unwnd_txq[TC_MAX_QUEUE];
> +
> +	if (sch->parent != TC_H_ROOT)
> +		return -EOPNOTSUPP;
> +
> +	if (!netif_is_multiqueue(dev))
> +		return -EOPNOTSUPP;
> +
> +	if (nla_len(opt) < sizeof(*qopt))
> +		return -EINVAL;
> +	qopt = nla_data(opt);
> +
> +	memcpy(unwnd_map, dev->prio_tc_map, sizeof(unwnd_map));
> +	memcpy(unwnd_txq, dev->tc_to_txq, sizeof(unwnd_txq));
> +
> +	/* If the mqprio options indicate that hardware should own
> +	 * the queue mapping then run ndo_setup_tc if this can not
> +	 * be done fail immediately.
> +	 */
> +	if (qopt->hw && dev->netdev_ops->ndo_setup_tc) {
> +		priv->hw_owned = 1;
> +		err = dev->netdev_ops->ndo_setup_tc(dev, qopt->num_tc);
> +		if (err)
> +			return err;
> +	} else if (!qopt->hw) {
> +		if (mqprio_parse_opt(dev, qopt))
> +			return -EINVAL;
> +
> +		if (netdev_set_num_tc(dev, qopt->num_tc))
> +			return -EINVAL;
> +
> +		for (i = 0; i < qopt->num_tc; i++)
> +			netdev_set_tc_queue(dev, i,
> +					    qopt->count[i], qopt->offset[i]);
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	/* Always use supplied priority mappings */
> +	for (i = 0; i < TC_BITMASK+1; i++) {

	for (i = 0; i < TC_BITMASK + 1; i++) {

> +		if (netdev_set_prio_tc_map(dev, i, qopt->prio_tc_map[i])) {
> +			err = -EINVAL;
> +			goto tc_err;
> +		}
> +	}
> +
> +	/* pre-allocate qdisc, attachment can't fail */
> +	priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
> +			       GFP_KERNEL);
> +	if (priv->qdiscs == NULL) {
> +		err = -ENOMEM;
> +		goto tc_err;
> +	}
> +
> +	for (i = 0; i < dev->num_tx_queues; i++) {
> +		dev_queue = netdev_get_tx_queue(dev, i);
> +		qdisc = qdisc_create_dflt(dev_queue, &pfifo_fast_ops,
> +					  TC_H_MAKE(TC_H_MAJ(sch->handle),
> +						    TC_H_MIN(i + 1)));
> +		if (qdisc == NULL) {
> +			err = -ENOMEM;
> +			goto err;
> +		}
> +		qdisc->flags |= TCQ_F_CAN_BYPASS;
> +		priv->qdiscs[i] = qdisc;
> +	}
> +
> +	sch->flags |= TCQ_F_MQROOT;
> +	return 0;
> +
> +err:
> +	mqprio_destroy(sch);
> +tc_err:
> +	if (priv->hw_owned)
> +		dev->netdev_ops->ndo_setup_tc(dev, unwnd_tc);
> +	else
> +		netdev_set_num_tc(dev, unwnd_tc);
> +
> +	memcpy(dev->prio_tc_map, unwnd_map, sizeof(unwnd_map));
> +	memcpy(dev->tc_to_txq, unwnd_txq, sizeof(unwnd_txq));
> +
> +	return err;
> +}
> +
> +static void mqprio_attach(struct Qdisc *sch)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	struct Qdisc *qdisc;
> +	unsigned int ntx;
> +
> +	/* Attach underlying qdisc */
> +	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
> +		qdisc = priv->qdiscs[ntx];
> +		qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
> +		if (qdisc)
> +			qdisc_destroy(qdisc);
> +	}
> +	kfree(priv->qdiscs);
> +	priv->qdiscs = NULL;
> +}
> +
> +static struct netdev_queue *mqprio_queue_get(struct Qdisc *sch,
> +					     unsigned long cl)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	unsigned long ntx = cl - 1;
> +
> +	if (ntx >= dev->num_tx_queues)
> +		return NULL;
> +	return netdev_get_tx_queue(dev, ntx);
> +}
> +
> +static int mqprio_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
> +		    struct Qdisc **old)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
> +
> +	if (dev->flags & IFF_UP)
> +		dev_deactivate(dev);
> +
> +	*old = dev_graft_qdisc(dev_queue, new);
> +
> +	if (dev->flags & IFF_UP)
> +		dev_activate(dev);
> +
> +	return 0;
> +}
> +
> +static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	struct mqprio_sched *priv = qdisc_priv(sch);
> +	unsigned char *b = skb_tail_pointer(skb);
> +	struct tc_mqprio_qopt opt;
> +	struct Qdisc *qdisc;
> +	unsigned int i;
> +
> +	sch->q.qlen = 0;
> +	memset(&sch->bstats, 0, sizeof(sch->bstats));
> +	memset(&sch->qstats, 0, sizeof(sch->qstats));
> +
> +	for (i = 0; i < dev->num_tx_queues; i++) {
> +		qdisc = netdev_get_tx_queue(dev, i)->qdisc;
> +		spin_lock_bh(qdisc_lock(qdisc));
> +		sch->q.qlen		+= qdisc->q.qlen;
> +		sch->bstats.bytes	+= qdisc->bstats.bytes;
> +		sch->bstats.packets	+= qdisc->bstats.packets;
> +		sch->qstats.qlen	+= qdisc->qstats.qlen;
> +		sch->qstats.backlog	+= qdisc->qstats.backlog;
> +		sch->qstats.drops	+= qdisc->qstats.drops;
> +		sch->qstats.requeues	+= qdisc->qstats.requeues;
> +		sch->qstats.overlimits	+= qdisc->qstats.overlimits;
> +		spin_unlock_bh(qdisc_lock(qdisc));
> +	}
> +
> +	opt.num_tc = dev->num_tc;
> +	memcpy(opt.prio_tc_map, dev->prio_tc_map, 16);

s/16/TC_SOMETHING

> +	opt.hw = priv->hw_owned;
> +
> +	for (i = 0; i < dev->num_tc; i++) {
> +		opt.count[i] = dev->tc_to_txq[i].count;
> +		opt.offset[i] = dev->tc_to_txq[i].offset;
> +	}
> +
> +	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
> +
> +	return skb->len;
> +nla_put_failure:
> +	nlmsg_trim(skb, b);
> +	return -1;
> +}
> +
> +static struct Qdisc *mqprio_leaf(struct Qdisc *sch, unsigned long cl)
> +{
> +	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
> +
> +	return dev_queue->qdisc_sleeping;
> +}
> +
> +static unsigned long mqprio_get(struct Qdisc *sch, u32 classid)
> +{
> +	unsigned int ntx = TC_H_MIN(classid);
> +
> +	if (!mqprio_queue_get(sch, ntx))
> +		return 0;
> +	return ntx;
> +}
> +
> +static void mqprio_put(struct Qdisc *sch, unsigned long cl)
> +{
> +}
> +
> +static int mqprio_dump_class(struct Qdisc *sch, unsigned long cl,
> +			 struct sk_buff *skb, struct tcmsg *tcm)
> +{
> +	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
> +
> +	tcm->tcm_parent = TC_H_ROOT;
> +	tcm->tcm_handle |= TC_H_MIN(cl);
> +	tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
> +	return 0;
> +}
> +
> +static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
> +			       struct gnet_dump *d)
> +{
> +	struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
> +
> +	sch = dev_queue->qdisc_sleeping;
> +	sch->qstats.qlen = sch->q.qlen;
> +	if (gnet_stats_copy_basic(d, &sch->bstats) < 0 ||
> +	    gnet_stats_copy_queue(d, &sch->qstats) < 0)
> +		return -1;
> +	return 0;
> +}
> +
> +static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
> +{
> +	struct net_device *dev = qdisc_dev(sch);
> +	unsigned long ntx;
> +
> +	if (arg->stop)
> +		return;
> +
> +	arg->count = arg->skip;
> +	for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {

Did you give up those stats per tc class? You only show the leaf
classes here, but you could first loop per num_tc (as virtual
parent classes). So in dump_class_stats you should be able to
distinguish class 'level' by cl and do the second loop if necessary.
To show the class hierarchy you change tcm_parent in dump_class
for 'leaf' classes (like eg in sch_htb/htb_dump_class).

Jarek P.

> +		if (arg->fn(sch, ntx + 1, arg) < 0) {
> +			arg->stop = 1;
> +			break;
> +		}
> +		arg->count++;
> +	}
> +}
> +
> +static const struct Qdisc_class_ops mqprio_class_ops = {
> +	.graft		= mqprio_graft,
> +	.leaf		= mqprio_leaf,
> +	.get		= mqprio_get,
> +	.put		= mqprio_put,
> +	.walk		= mqprio_walk,
> +	.dump		= mqprio_dump_class,
> +	.dump_stats	= mqprio_dump_class_stats,
> +};
> +
> +struct Qdisc_ops mqprio_qdisc_ops __read_mostly = {
> +	.cl_ops		= &mqprio_class_ops,
> +	.id		= "mqprio",
> +	.priv_size	= sizeof(struct mqprio_sched),
> +	.init		= mqprio_init,
> +	.destroy	= mqprio_destroy,
> +	.attach		= mqprio_attach,
> +	.dump		= mqprio_dump,
> +	.owner		= THIS_MODULE,
> +};
> +
> +static int __init mqprio_module_init(void)
> +{
> +	return register_qdisc(&mqprio_qdisc_ops);
> +}
> +
> +static void __exit mqprio_module_exit(void)
> +{
> +	unregister_qdisc(&mqprio_qdisc_ops);
> +}
> +
> +module_init(mqprio_module_init);
> +module_exit(mqprio_module_exit);
> +
> +MODULE_LICENSE("GPL");
> 

Re: [net-next-2.6 PATCH v4 1/2] net: implement mechanism for HW based QOS

[jamal]

On Mon, 2011-01-03 at 19:05 -0800, John Fastabend wrote:
[..]

> To steer the skb we mask out the lower 4 bits of the priority
> and allow the hardware to configure upto 15 distinct classes
> of traffic. This is expected to be sufficient for most applications
> at any rate it is more then the 8021Q spec designates and is
> equal to the number of prio bands currently implemented in
> the default qdisc.

This seems very hardware specific.
i.e may be true for 8021q (or like 8021q) type hardware and therefore
your qdisc. 
There are people with hardware that has thousands of hardware
flow queues (or at least give impressions as such). Maybe a naming
convention prefixed with 8021Q would be nicer or moving it into
your qdisc infrastructure and export it so drivers needing it can.

cheers,
jamal

Re: [net-next-2.6 PATCH v4 2/2] net_sched: implement a root container qdisc sch_mclass

[John Fastabend]

On 1/4/2011 3:18 AM, Jarek Poplawski wrote:
> On Mon, Jan 03, 2011 at 07:05:58PM -0800, John Fastabend wrote:
>> This implements a mqprio queueing discipline that by default creates
>> a pfifo_fast qdisc per tx queue and provides the needed configuration
>> interface.
>>
>> Using the mqprio qdisc the number of tcs currently in use along
>> with the range of queues alloted to each class can be configured. By
>> default skbs are mapped to traffic classes using the skb priority.
>> This mapping is configurable.
>>
>> Configurable parameters,
>>
>> struct tc_mclass_qopt {
> 
> Now *_mqprio here and in the subject of the message.
> 
>>         __u8    num_tc;
>>         __u8    prio_tc_map[16];
> 
> s/16/TC_SOMETHING/
> 
>>         __u8    hw;
>>         __u16   count[16];
>>         __u16   offset[16];
>> };
>>
>> Here the count/offset pairing give the queue alignment and the
>> prio_tc_map gives the mapping from skb->priority to tc.
>>
>> The hw bit determines if the hardware should configure the count
>> and offset values. If the hardware bit is set then the operation
>> will fail if the hardware does not implement the ndo_setup_tc
>> operation. This is to avoid undetermined states where the hardware
>> may or may not control the queue mapping. Also minimal bounds
>> checking is done on the count/offset to verify a queue does not
>> exceed num_tx_queues and that queue ranges do not overlap. Otherwise
>> it is left to user policy or hardware configuration to create
>> useful mappings.
>>
>> It is expected that hardware QOS schemes can be implemented by
>> creating appropriate mappings of queues in ndo_tc_setup().
>>
>> One expected use case is drivers will use the ndo_setup_tc to map
>> queue ranges onto 802.1Q traffic classes. This provides a generic
>> mechanism to map network traffic onto these traffic classes and
>> removes the need for lower layer drivers to no specifics about
>> traffic types.
>>
>> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
>> ---
>>
>>  include/linux/netdevice.h |    3
>>  include/linux/pkt_sched.h |    9 +
>>  net/sched/Kconfig         |   10 +
>>  net/sched/Makefile        |    1
>>  net/sched/sch_generic.c   |    4 +
>>  net/sched/sch_mqprio.c    |  357 +++++++++++++++++++++++++++++++++++++++++++++
>>  6 files changed, 384 insertions(+), 0 deletions(-)
>>  create mode 100644 net/sched/sch_mqprio.c
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 073c48d..f90a863 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -764,6 +764,8 @@ struct netdev_tc_txq {
>>   * int (*ndo_set_vf_port)(struct net_device *dev, int vf,
>>   *                     struct nlattr *port[]);
>>   * int (*ndo_get_vf_port)(struct net_device *dev, int vf, struct sk_buff *skb);
>> + *
>> + * int (*ndo_setup_tc)(struct net_device *dev, int tc);
>>   */
>>  #define HAVE_NET_DEVICE_OPS
>>  struct net_device_ops {
>> @@ -822,6 +824,7 @@ struct net_device_ops {
>>                                                  struct nlattr *port[]);
>>       int                     (*ndo_get_vf_port)(struct net_device *dev,
>>                                                  int vf, struct sk_buff *skb);
>> +     int                     (*ndo_setup_tc)(struct net_device *dev, u8 tc);
>>  #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
>>       int                     (*ndo_fcoe_enable)(struct net_device *dev);
>>       int                     (*ndo_fcoe_disable)(struct net_device *dev);
>> diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
>> index 2cfa4bc..8e29fa6 100644
>> --- a/include/linux/pkt_sched.h
>> +++ b/include/linux/pkt_sched.h
>> @@ -481,4 +481,13 @@ struct tc_drr_stats {
>>       __u32   deficit;
>>  };
>>
>> +/* MCLASS */
> 
> /* MQPRIO */
> 
>> +struct tc_mqprio_qopt {
>> +     __u8    num_tc;
>> +     __u8    prio_tc_map[16];
>> +     __u8    hw;
>> +     __u16   count[16];
>> +     __u16   offset[16];
> 
> s/16/TC_SOMETHING/

fixed.

> 
>> +};
>> +
>>  #endif
>> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
>> index a36270a..e42853b 100644
>> --- a/net/sched/Kconfig
>> +++ b/net/sched/Kconfig
>> @@ -205,6 +205,16 @@ config NET_SCH_DRR
>>
>>         If unsure, say N.
>>
>> +config NET_SCH_MQPRIO
>> +     tristate "Multi-queue priority scheduler (MQPRIO)"
>> +     help
>> +       Say Y here if you want to use the Multi-queue Priority scheduler.
> 
> We might mention about a proper NIC required.
> 

Probably good to add a note here. Although you could use qdisc without NIC support.

>> +
>> +       To compile this driver as a module, choose M here: the module will
>> +       be called sch_mqprio.
>> +
>> +       If unsure, say N.
>> +
>>  config NET_SCH_INGRESS
>>       tristate "Ingress Qdisc"
>>       depends on NET_CLS_ACT
>> diff --git a/net/sched/Makefile b/net/sched/Makefile
>> index 960f5db..26ce681 100644
>> --- a/net/sched/Makefile
>> +++ b/net/sched/Makefile
>> @@ -32,6 +32,7 @@ obj-$(CONFIG_NET_SCH_MULTIQ)        += sch_multiq.o
>>  obj-$(CONFIG_NET_SCH_ATM)    += sch_atm.o
>>  obj-$(CONFIG_NET_SCH_NETEM)  += sch_netem.o
>>  obj-$(CONFIG_NET_SCH_DRR)    += sch_drr.o
>> +obj-$(CONFIG_NET_SCH_MQPRIO) += sch_mqprio.o
>>  obj-$(CONFIG_NET_CLS_U32)    += cls_u32.o
>>  obj-$(CONFIG_NET_CLS_ROUTE4) += cls_route.o
>>  obj-$(CONFIG_NET_CLS_FW)     += cls_fw.o
>> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
>> index 34dc598..723b278 100644
>> --- a/net/sched/sch_generic.c
>> +++ b/net/sched/sch_generic.c
>> @@ -540,6 +540,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
>>       .dump           =       pfifo_fast_dump,
>>       .owner          =       THIS_MODULE,
>>  };
>> +EXPORT_SYMBOL(pfifo_fast_ops);
>>
>>  struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
>>                         struct Qdisc_ops *ops)
>> @@ -674,6 +675,7 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
>>
>>       return oqdisc;
>>  }
>> +EXPORT_SYMBOL(dev_graft_qdisc);
>>
>>  static void attach_one_default_qdisc(struct net_device *dev,
>>                                    struct netdev_queue *dev_queue,
>> @@ -761,6 +763,7 @@ void dev_activate(struct net_device *dev)
>>               dev_watchdog_up(dev);
>>       }
>>  }
>> +EXPORT_SYMBOL(dev_activate);
>>
>>  static void dev_deactivate_queue(struct net_device *dev,
>>                                struct netdev_queue *dev_queue,
>> @@ -840,6 +843,7 @@ void dev_deactivate(struct net_device *dev)
>>       list_add(&dev->unreg_list, &single);
>>       dev_deactivate_many(&single);
>>  }
>> +EXPORT_SYMBOL(dev_deactivate);
>>
>>  static void dev_init_scheduler_queue(struct net_device *dev,
>>                                    struct netdev_queue *dev_queue,
>> diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
>> new file mode 100644
>> index 0000000..e9e74c7
>> --- /dev/null
>> +++ b/net/sched/sch_mqprio.c
>> @@ -0,0 +1,357 @@
>> +/*
>> + * net/sched/sch_mqprio.c
>> + *
>> + * Copyright (c) 2010 John Fastabend <john.r.fastabend@intel.com>
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License
>> + * version 2 as published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/types.h>
>> +#include <linux/slab.h>
>> +#include <linux/kernel.h>
>> +#include <linux/string.h>
>> +#include <linux/errno.h>
>> +#include <linux/skbuff.h>
>> +#include <net/netlink.h>
>> +#include <net/pkt_sched.h>
>> +#include <net/sch_generic.h>
>> +
>> +struct mqprio_sched {
>> +     struct Qdisc            **qdiscs;
>> +     int hw_owned;
>> +};
>> +
>> +static void mqprio_destroy(struct Qdisc *sch)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     struct mqprio_sched *priv = qdisc_priv(sch);
>> +     unsigned int ntx;
>> +
>> +     if (!priv->qdiscs)
>> +             return;
>> +
>> +     for (ntx = 0; ntx < dev->num_tx_queues && priv->qdiscs[ntx]; ntx++)
>> +             qdisc_destroy(priv->qdiscs[ntx]);
>> +
>> +     if (priv->hw_owned && dev->netdev_ops->ndo_setup_tc)
>> +             dev->netdev_ops->ndo_setup_tc(dev, 0);
>> +     else
>> +             netdev_set_num_tc(dev, 0);
> 
> I'm not sure why this unsetting is needed in case it was set by a
> driver before mqprio was created.
> 

ndo_setup_tc(dev,x) is called at init to be symetric I think we need to call it here as well. Otherwise we could leave num_tc set unecessarily. Maybe saving the original value and setting it back to the orignal num_tc would be more correct.

>> +
>> +     kfree(priv->qdiscs);
>> +}
>> +
>> +static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
>> +{
>> +     int i, j;
>> +
>> +     /* Verify num_tc is not out of max range */
>> +     if (qopt->num_tc > TC_MAX_QUEUE)
>> +             return -EINVAL;
>> +
>> +     for (i = 0; i < qopt->num_tc; i++) {
>> +             unsigned int last = qopt->offset[i] + qopt->count[i];
>> +             /* Verify the queue offset is in the num tx range */
>> +             if (qopt->offset[i] >= dev->num_tx_queues)
>> +                     return -EINVAL;
>> +             /* Verify the queue count is in tx range being equal to the
>> +              * num_tx_queues indicates the last queue is in use.
>> +              */
>> +             else if (last > dev->num_tx_queues)
>> +                     return -EINVAL;
>> +
>> +             /* Verify that the offset and counts do not overlap */
>> +             for (j = i + 1; j < qopt->num_tc; j++) {
>> +                     if (last > qopt->offset[j])
>> +                             return -EINVAL;
>> +             }
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static int mqprio_init(struct Qdisc *sch, struct nlattr *opt)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     struct mqprio_sched *priv = qdisc_priv(sch);
>> +     struct netdev_queue *dev_queue;
>> +     struct Qdisc *qdisc;
>> +     int i, err = -EOPNOTSUPP;
>> +     struct tc_mqprio_qopt *qopt = NULL;
>> +
>> +     /* Unwind attributes on failure */
>> +     u8 unwnd_tc = dev->num_tc;
>> +     u8 unwnd_map[TC_BITMASK+1];
> 
>         u8 unwnd_map[TC_BITMASK + 1];
> 

fixed

>> +     struct netdev_tc_txq unwnd_txq[TC_MAX_QUEUE];
>> +
>> +     if (sch->parent != TC_H_ROOT)
>> +             return -EOPNOTSUPP;
>> +
>> +     if (!netif_is_multiqueue(dev))
>> +             return -EOPNOTSUPP;
>> +
>> +     if (nla_len(opt) < sizeof(*qopt))
>> +             return -EINVAL;
>> +     qopt = nla_data(opt);
>> +
>> +     memcpy(unwnd_map, dev->prio_tc_map, sizeof(unwnd_map));
>> +     memcpy(unwnd_txq, dev->tc_to_txq, sizeof(unwnd_txq));
>> +
>> +     /* If the mqprio options indicate that hardware should own
>> +      * the queue mapping then run ndo_setup_tc if this can not
>> +      * be done fail immediately.
>> +      */
>> +     if (qopt->hw && dev->netdev_ops->ndo_setup_tc) {
>> +             priv->hw_owned = 1;
>> +             err = dev->netdev_ops->ndo_setup_tc(dev, qopt->num_tc);
>> +             if (err)
>> +                     return err;
>> +     } else if (!qopt->hw) {
>> +             if (mqprio_parse_opt(dev, qopt))
>> +                     return -EINVAL;
>> +
>> +             if (netdev_set_num_tc(dev, qopt->num_tc))
>> +                     return -EINVAL;
>> +
>> +             for (i = 0; i < qopt->num_tc; i++)
>> +                     netdev_set_tc_queue(dev, i,
>> +                                         qopt->count[i], qopt->offset[i]);
>> +     } else {
>> +             return -EINVAL;
>> +     }
>> +
>> +     /* Always use supplied priority mappings */
>> +     for (i = 0; i < TC_BITMASK+1; i++) {
> 
>         for (i = 0; i < TC_BITMASK + 1; i++) {
> 

fixed.

>> +             if (netdev_set_prio_tc_map(dev, i, qopt->prio_tc_map[i])) {
>> +                     err = -EINVAL;
>> +                     goto tc_err;
>> +             }
>> +     }
>> +
>> +     /* pre-allocate qdisc, attachment can't fail */
>> +     priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
>> +                            GFP_KERNEL);
>> +     if (priv->qdiscs == NULL) {
>> +             err = -ENOMEM;
>> +             goto tc_err;
>> +     }
>> +
>> +     for (i = 0; i < dev->num_tx_queues; i++) {
>> +             dev_queue = netdev_get_tx_queue(dev, i);
>> +             qdisc = qdisc_create_dflt(dev_queue, &pfifo_fast_ops,
>> +                                       TC_H_MAKE(TC_H_MAJ(sch->handle),
>> +                                                 TC_H_MIN(i + 1)));
>> +             if (qdisc == NULL) {
>> +                     err = -ENOMEM;
>> +                     goto err;
>> +             }
>> +             qdisc->flags |= TCQ_F_CAN_BYPASS;
>> +             priv->qdiscs[i] = qdisc;
>> +     }
>> +
>> +     sch->flags |= TCQ_F_MQROOT;
>> +     return 0;
>> +
>> +err:
>> +     mqprio_destroy(sch);
>> +tc_err:
>> +     if (priv->hw_owned)
>> +             dev->netdev_ops->ndo_setup_tc(dev, unwnd_tc);
>> +     else
>> +             netdev_set_num_tc(dev, unwnd_tc);
>> +
>> +     memcpy(dev->prio_tc_map, unwnd_map, sizeof(unwnd_map));
>> +     memcpy(dev->tc_to_txq, unwnd_txq, sizeof(unwnd_txq));
>> +
>> +     return err;
>> +}
>> +
>> +static void mqprio_attach(struct Qdisc *sch)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     struct mqprio_sched *priv = qdisc_priv(sch);
>> +     struct Qdisc *qdisc;
>> +     unsigned int ntx;
>> +
>> +     /* Attach underlying qdisc */
>> +     for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
>> +             qdisc = priv->qdiscs[ntx];
>> +             qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
>> +             if (qdisc)
>> +                     qdisc_destroy(qdisc);
>> +     }
>> +     kfree(priv->qdiscs);
>> +     priv->qdiscs = NULL;
>> +}
>> +
>> +static struct netdev_queue *mqprio_queue_get(struct Qdisc *sch,
>> +                                          unsigned long cl)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     unsigned long ntx = cl - 1;
>> +
>> +     if (ntx >= dev->num_tx_queues)
>> +             return NULL;
>> +     return netdev_get_tx_queue(dev, ntx);
>> +}
>> +
>> +static int mqprio_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
>> +                 struct Qdisc **old)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
>> +
>> +     if (dev->flags & IFF_UP)
>> +             dev_deactivate(dev);
>> +
>> +     *old = dev_graft_qdisc(dev_queue, new);
>> +
>> +     if (dev->flags & IFF_UP)
>> +             dev_activate(dev);
>> +
>> +     return 0;
>> +}
>> +
>> +static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     struct mqprio_sched *priv = qdisc_priv(sch);
>> +     unsigned char *b = skb_tail_pointer(skb);
>> +     struct tc_mqprio_qopt opt;
>> +     struct Qdisc *qdisc;
>> +     unsigned int i;
>> +
>> +     sch->q.qlen = 0;
>> +     memset(&sch->bstats, 0, sizeof(sch->bstats));
>> +     memset(&sch->qstats, 0, sizeof(sch->qstats));
>> +
>> +     for (i = 0; i < dev->num_tx_queues; i++) {
>> +             qdisc = netdev_get_tx_queue(dev, i)->qdisc;
>> +             spin_lock_bh(qdisc_lock(qdisc));
>> +             sch->q.qlen             += qdisc->q.qlen;
>> +             sch->bstats.bytes       += qdisc->bstats.bytes;
>> +             sch->bstats.packets     += qdisc->bstats.packets;
>> +             sch->qstats.qlen        += qdisc->qstats.qlen;
>> +             sch->qstats.backlog     += qdisc->qstats.backlog;
>> +             sch->qstats.drops       += qdisc->qstats.drops;
>> +             sch->qstats.requeues    += qdisc->qstats.requeues;
>> +             sch->qstats.overlimits  += qdisc->qstats.overlimits;
>> +             spin_unlock_bh(qdisc_lock(qdisc));
>> +     }
>> +
>> +     opt.num_tc = dev->num_tc;
>> +     memcpy(opt.prio_tc_map, dev->prio_tc_map, 16);
> 
> s/16/TC_SOMETHING

fixed

> 
>> +     opt.hw = priv->hw_owned;
>> +
>> +     for (i = 0; i < dev->num_tc; i++) {
>> +             opt.count[i] = dev->tc_to_txq[i].count;
>> +             opt.offset[i] = dev->tc_to_txq[i].offset;
>> +     }
>> +
>> +     NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
>> +
>> +     return skb->len;
>> +nla_put_failure:
>> +     nlmsg_trim(skb, b);
>> +     return -1;
>> +}
>> +
>> +static struct Qdisc *mqprio_leaf(struct Qdisc *sch, unsigned long cl)
>> +{
>> +     struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
>> +
>> +     return dev_queue->qdisc_sleeping;
>> +}
>> +
>> +static unsigned long mqprio_get(struct Qdisc *sch, u32 classid)
>> +{
>> +     unsigned int ntx = TC_H_MIN(classid);
>> +
>> +     if (!mqprio_queue_get(sch, ntx))
>> +             return 0;
>> +     return ntx;
>> +}
>> +
>> +static void mqprio_put(struct Qdisc *sch, unsigned long cl)
>> +{
>> +}
>> +
>> +static int mqprio_dump_class(struct Qdisc *sch, unsigned long cl,
>> +                      struct sk_buff *skb, struct tcmsg *tcm)
>> +{
>> +     struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
>> +
>> +     tcm->tcm_parent = TC_H_ROOT;
>> +     tcm->tcm_handle |= TC_H_MIN(cl);
>> +     tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
>> +     return 0;
>> +}
>> +
>> +static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
>> +                            struct gnet_dump *d)
>> +{
>> +     struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
>> +
>> +     sch = dev_queue->qdisc_sleeping;
>> +     sch->qstats.qlen = sch->q.qlen;
>> +     if (gnet_stats_copy_basic(d, &sch->bstats) < 0 ||
>> +         gnet_stats_copy_queue(d, &sch->qstats) < 0)
>> +             return -1;
>> +     return 0;
>> +}
>> +
>> +static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
>> +{
>> +     struct net_device *dev = qdisc_dev(sch);
>> +     unsigned long ntx;
>> +
>> +     if (arg->stop)
>> +             return;
>> +
>> +     arg->count = arg->skip;
>> +     for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
> 
> Did you give up those stats per tc class? You only show the leaf
> classes here, but you could first loop per num_tc (as virtual
> parent classes). So in dump_class_stats you should be able to
> distinguish class 'level' by cl and do the second loop if necessary.
> To show the class hierarchy you change tcm_parent in dump_class
> for 'leaf' classes (like eg in sch_htb/htb_dump_class).
> 

I did give up... but got it working with your hint in v5 thanks.

John.