[UPDATED] [NET-NEXT PATCH 1/2] pkt_sched: Add multiqueue scheduler support

Jeff Kirsher
2008-08-30T07:21:40Z

From: Alexander Duyck <alexander.h.duyck@intel.com>

This patch is intended to add a qdisc to support the new tx multiqueue
architecture by providing a band for each hardware queue. By doing
this it is possible to support a different qdisc per physical hardware
queue.

This qdisc uses the skb->queue_mapping to select which band to place
the traffic onto. It then uses a round robin w/ a check to see if the
subqueue is stopped to determine which band to dequeue the packet from.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---

include/linux/pkt_sched.h | 6 +
net/sched/Kconfig | 9 +
net/sched/Makefile | 1
net/sched/sch_multiq.c | 470 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 486 insertions(+), 0 deletions(-)
create mode 100644 net/sched/sch_multiq.c

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index e5de421..7fbc952 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -123,6 +123,12 @@ struct tc_prio_qopt
__u8 priomap[TC_PRIO_MAX+1]; /* Map: logical priority -> PRIO band */
};

+/* MULTIQ section */
+
+struct tc_multiq_qopt {
+ int bands; /* Number of bands */
+};
+
/* TBF section */

struct tc_tbf_qopt
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 9437b27..efaa7a7 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -106,6 +106,15 @@ config NET_SCH_PRIO
To compile this code as a module, choose M here: the
module will be called sch_prio.

+config NET_SCH_MULTIQ
+ tristate "Hardware Multiqueue-aware Multi Band Queuing (MULTIQ)"
+ ---help---
+ Say Y here if you want to use an n-band queue packet scheduler
+ to support devices that have multiple hardware transmit queues.
+
+ To compile this code as a module, choose M here: the
+ module will be called sch_multiq.
+
config NET_SCH_RED
tristate "Random Early Detection (RED)"
---help---
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 1d2b0f7..3d9b953 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_NET_SCH_SFQ) += sch_sfq.o
obj-$(CONFIG_NET_SCH_TBF) += sch_tbf.o
obj-$(CONFIG_NET_SCH_TEQL) += sch_teql.o
obj-$(CONFIG_NET_SCH_PRIO) += sch_prio.o
+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_CLS_U32) += cls_u32.o
diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
new file mode 100644
index 0000000..708dd5c
--- /dev/null
+++ b/net/sched/sch_multiq.c
@@ -0,0 +1,470 @@
+/*
+ * net/sched/sch_multiq.c
+ * This qdisc is based off of the rr qdisc and is meant to
+ * prevent head-of-line blocking on devices that have multiple
+ * hardware queues.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Authors: Alexander Duyck <alexander.h.duyck@intel.com>
+ */
+
+#include <linux/module.h>
+#include <linux/types.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>
+
+
+struct multiq_sched_data {
+ int bands;
+ int curband;
+ struct tcf_proto *filter_list;
+ struct Qdisc **queues;
+
+};
+
+
+static struct Qdisc *
+multiq_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ u32 band;
+ struct tcf_result res;
+ int err;
+
+ *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
+ err = tc_classify(skb, q->filter_list, &res);
+#ifdef CONFIG_NET_CLS_ACT
+ switch (err) {
+ case TC_ACT_STOLEN:
+ case TC_ACT_QUEUED:
+ *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
+ case TC_ACT_SHOT:
+ return NULL;
+ }
+#endif
+ band = skb_get_queue_mapping(skb);
+
+ if (band >= q->bands)
+ return q->queues[0];
+
+ return q->queues[band];
+}
+
+static int
+multiq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+ struct Qdisc *qdisc;
+ int ret;
+
+ qdisc = multiq_classify(skb, sch, &ret);
+#ifdef CONFIG_NET_CLS_ACT
+ if (qdisc == NULL) {
+
+ if (ret & __NET_XMIT_BYPASS)
+ sch->qstats.drops++;
+ kfree_skb(skb);
+ return ret;
+ }
+#endif
+
+ ret = qdisc_enqueue(skb, qdisc);
+ if (ret == NET_XMIT_SUCCESS) {
+ sch->bstats.bytes += qdisc_pkt_len(skb);
+ sch->bstats.packets++;
+ sch->q.qlen++;
+ return NET_XMIT_SUCCESS;
+ }
+ if (net_xmit_drop_count(ret))
+ sch->qstats.drops++;
+ return ret;
+}
+
+
+static int
+multiq_requeue(struct sk_buff *skb, struct Qdisc *sch)
+{
+ struct Qdisc *qdisc;
+ int ret;
+
+ qdisc = multiq_classify(skb, sch, &ret);
+#ifdef CONFIG_NET_CLS_ACT
+ if (qdisc == NULL) {
+ if (ret & __NET_XMIT_BYPASS)
+ sch->qstats.drops++;
+ kfree_skb(skb);
+ return ret;
+ }
+#endif
+
+ ret = qdisc->ops->requeue(skb, qdisc);
+ if (ret == NET_XMIT_SUCCESS) {
+ sch->q.qlen++;
+ sch->qstats.requeues++;
+ return NET_XMIT_SUCCESS;
+ }
+ if (net_xmit_drop_count(ret))
+ sch->qstats.drops++;
+ return ret;
+}
+
+
+static struct sk_buff *multiq_dequeue(struct Qdisc *sch)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ struct Qdisc *qdisc;
+ struct sk_buff *skb;
+ int band;
+
+ for (band = 0; band < q->bands; band++) {
+ /* cycle through bands to ensure fairness */
+ q->curband++;
+ if (q->curband >= q->bands)
+ q->curband = 0;
+
+ /* Check that target subqueue is available before
+ * pulling an skb to avoid excessive requeues
+ */
+ if (!__netif_subqueue_stopped(qdisc_dev(sch), q->curband)) {
+ qdisc = q->queues[q->curband];
+ skb = qdisc->dequeue(qdisc);
+ if (skb) {
+ sch->q.qlen--;
+ return skb;
+ }
+ }
+ }
+ return NULL;
+
+}
+
+static unsigned int multiq_drop(struct Qdisc *sch)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ int band;
+ unsigned int len;
+ struct Qdisc *qdisc;
+
+ for (band = q->bands-1; band >= 0; band--) {
+ qdisc = q->queues[band];
+ if (qdisc->ops->drop) {
+ len = qdisc->ops->drop(qdisc);
+ if (len != 0) {
+ sch->q.qlen--;
+ return len;
+ }
+ }
+ }
+ return 0;
+}
+
+
+static void
+multiq_reset(struct Qdisc *sch)
+{
+ int band;
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ for (band = 0; band < q->bands; band++)
+ qdisc_reset(q->queues[band]);
+ sch->q.qlen = 0;
+}
+
+static void
+multiq_destroy(struct Qdisc *sch)
+{
+ int band;
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ tcf_destroy_chain(&q->filter_list);
+ for (band = 0; band < q->bands; band++)
+ qdisc_destroy(q->queues[band]);
+
+ kfree(q->queues);
+}
+
+static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ struct tc_multiq_qopt *qopt;
+ struct Qdisc **queues;
+ int i;
+
+ if (sch->parent != TC_H_ROOT)
+ return -EINVAL;
+ if (!netif_is_multiqueue(qdisc_dev(sch)))
+ return -EINVAL;
+ if (nla_len(opt) < sizeof(*qopt))
+ return -EINVAL;
+
+ qopt = nla_data(opt);
+
+ qopt->bands = qdisc_dev(sch)->real_num_tx_queues;
+
+ queues = kzalloc(sizeof(struct Qdisc *)*qopt->bands, GFP_KERNEL);
+ if (!queues)
+ return -ENOBUFS;
+
+ for (i = 0; i < qopt->bands; i++)
+ queues[i] = &noop_qdisc;
+
+ sch_tree_lock(sch);
+ q->queues = xchg(&queues, q->queues);
+ if (queues != NULL) {
+ for (i = 0; i < q->bands; i++) {
+ if (queues[i] != &noop_qdisc) {
+ qdisc_tree_decrease_qlen(queues[i],
+ queues[i]->q.qlen);
+ qdisc_destroy(queues[i]);
+ }
+ }
+ kfree(queues);
+
+ }
+ q->bands = qopt->bands;
+
+ sch_tree_unlock(sch);
+
+ for (i = 0; i < q->bands; i++) {
+ if (q->queues[i] == &noop_qdisc) {
+ struct Qdisc *child;
+ child = qdisc_create_dflt(qdisc_dev(sch),
+ sch->dev_queue,
+ &pfifo_qdisc_ops,
+ TC_H_MAKE(sch->handle,
+ i + 1));
+ if (child) {
+ sch_tree_lock(sch);
+ child = xchg(&q->queues[i], child);
+
+ if (child != &noop_qdisc) {
+ qdisc_tree_decrease_qlen(child,
+ child->q.qlen);
+ qdisc_destroy(child);
+ }
+ sch_tree_unlock(sch);
+ }
+ }
+ }
+ return 0;
+}
+
+static int multiq_init(struct Qdisc *sch, struct nlattr *opt)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ q->queues = NULL;
+
+ if (opt == NULL)
+ return -EINVAL;
+
+ return multiq_tune(sch, opt);
+}
+
+static int multiq_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ unsigned char *b = skb_tail_pointer(skb);
+ struct nlattr *nest;
+ struct tc_multiq_qopt opt;
+
+ opt.bands = q->bands;
+
+ nest = nla_nest_compat_start(skb, TCA_OPTIONS, sizeof(opt), &opt);
+ if (nest == NULL)
+ goto nla_put_failure;
+ nla_nest_compat_end(skb, nest);
+
+ return skb->len;
+
+nla_put_failure:
+ nlmsg_trim(skb, b);
+ return -1;
+}
+
+static int multiq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
+ struct Qdisc **old)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ unsigned long band = arg - 1;
+
+ if (band >= q->bands)
+ return -EINVAL;
+
+ if (new == NULL)
+ new = &noop_qdisc;
+
+ sch_tree_lock(sch);
+ *old = q->queues[band];
+ q->queues[band] = new;
+ qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
+ qdisc_reset(*old);
+ sch_tree_unlock(sch);
+
+ return 0;
+}
+
+static struct Qdisc *
+multiq_leaf(struct Qdisc *sch, unsigned long arg)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ unsigned long band = arg - 1;
+
+ if (band >= q->bands)
+ return NULL;
+
+ return q->queues[band];
+}
+
+static unsigned long multiq_get(struct Qdisc *sch, u32 classid)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ unsigned long band = TC_H_MIN(classid);
+
+ if (band - 1 >= q->bands)
+ return 0;
+ return band;
+}
+
+static unsigned long multiq_bind(struct Qdisc *sch, unsigned long parent,
+ u32 classid)
+{
+ return multiq_get(sch, classid);
+}
+
+
+static void multiq_put(struct Qdisc *q, unsigned long cl)
+{
+ return;
+}
+
+static int multiq_change(struct Qdisc *sch, u32 handle, u32 parent,
+ struct nlattr **tca, unsigned long *arg)
+{
+ unsigned long cl = *arg;
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ if (cl - 1 > q->bands)
+ return -ENOENT;
+ return 0;
+}
+
+static int multiq_delete(struct Qdisc *sch, unsigned long cl)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ if (cl - 1 > q->bands)
+ return -ENOENT;
+ return 0;
+}
+
+
+static int multiq_dump_class(struct Qdisc *sch, unsigned long cl,
+ struct sk_buff *skb, struct tcmsg *tcm)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ if (cl - 1 > q->bands)
+ return -ENOENT;
+ tcm->tcm_handle |= TC_H_MIN(cl);
+ if (q->queues[cl-1])
+ tcm->tcm_info = q->queues[cl-1]->handle;
+ return 0;
+}
+
+static int multiq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
+ struct gnet_dump *d)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ struct Qdisc *cl_q;
+
+ cl_q = q->queues[cl - 1];
+ if (gnet_stats_copy_basic(d, &cl_q->bstats) < 0 ||
+ gnet_stats_copy_queue(d, &cl_q->qstats) < 0)
+ return -1;
+
+ return 0;
+}
+
+static void multiq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+ int band;
+
+ if (arg->stop)
+ return;
+
+ for (band = 0; band < q->bands; band++) {
+ if (arg->count < arg->skip) {
+ arg->count++;
+ continue;
+ }
+ if (arg->fn(sch, band+1, arg) < 0) {
+ arg->stop = 1;
+ break;
+ }
+ arg->count++;
+ }
+}
+
+static struct tcf_proto **multiq_find_tcf(struct Qdisc *sch, unsigned long cl)
+{
+ struct multiq_sched_data *q = qdisc_priv(sch);
+
+ if (cl)
+ return NULL;
+ return &q->filter_list;
+}
+
+static const struct Qdisc_class_ops multiq_class_ops = {
+ .graft = multiq_graft,
+ .leaf = multiq_leaf,
+ .get = multiq_get,
+ .put = multiq_put,
+ .change = multiq_change,
+ .delete = multiq_delete,
+ .walk = multiq_walk,
+ .tcf_chain = multiq_find_tcf,
+ .bind_tcf = multiq_bind,
+ .unbind_tcf = multiq_put,
+ .dump = multiq_dump_class,
+ .dump_stats = multiq_dump_class_stats,
+};
+
+static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {
+ .next = NULL,
+ .cl_ops = &multiq_class_ops,
+ .id = "multiq",
+ .priv_size = sizeof(struct multiq_sched_data),
+ .enqueue = multiq_enqueue,
+ .dequeue = multiq_dequeue,
+ .requeue = multiq_requeue,
+ .drop = multiq_drop,
+ .init = multiq_init,
+ .reset = multiq_reset,
+ .destroy = multiq_destroy,
+ .change = multiq_tune,
+ .dump = multiq_dump,
+ .owner = THIS_MODULE,
+};
+
+static int __init multiq_module_init(void)
+{
+ return register_qdisc(&multiq_qdisc_ops);
+}
+
+static void __exit multiq_module_exit(void)
+{
+ unregister_qdisc(&multiq_qdisc_ops);
+}
+
+module_init(multiq_module_init)
+module_exit(multiq_module_exit)
+
+MODULE_LICENSE("GPL");