Re: [RFC PATCH v2 08/10] net: sched: pfifo_fast use alf_queue
From: Jesper Dangaard Brouer <hidden>
Date: 2016-07-14 15:11:53
On Wed, 13 Jul 2016 23:23:12 -0700 John Fastabend [off-list ref] wrote:
This converts the pfifo_fast qdisc to use the alf_queue enqueue and dequeue routines then sets the NOLOCK bit.
Should have said skb_array, not alf_queue ;-) > This also removes the logic used to pick the next band to dequeue from
quoted hunk ↗ jump to hunk
and instead just checks each alf_queue for packets from top priority to lowest. This might need to be a bit more clever but seems to work for now. Signed-off-by: John Fastabend <redacted> --- net/sched/sch_generic.c | 131 +++++++++++++++++++++++++++-------------------- 1 file changed, 75 insertions(+), 56 deletions(-)diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 7dcd066..2ac3eb9 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c@@ -26,6 +26,7 @@ #include <linux/list.h> #include <linux/slab.h> #include <linux/if_vlan.h> +#include <linux/skb_array.h> #include <net/sch_generic.h> #include <net/pkt_sched.h> #include <net/dst.h>@@ -555,88 +556,79 @@ static const u8 prio2band[TC_PRIO_MAX + 1] = { /* * Private data for a pfifo_fast scheduler containing: - * - queues for the three band - * - bitmap indicating which of the bands contain skbs + * - rings for priority bands */ struct pfifo_fast_priv { - u32 bitmap; - struct sk_buff_head q[PFIFO_FAST_BANDS]; + struct skb_array q[PFIFO_FAST_BANDS]; }; -/* - * Convert a bitmap to the first band number where an skb is queued, where: - * bitmap=0 means there are no skbs on any band. - * bitmap=1 means there is an skb on band 0. - * bitmap=7 means there are skbs on all 3 bands, etc. - */ -static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0}; - -static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv, - int band) +static inline struct skb_array *band2list(struct pfifo_fast_priv *priv, + int band) { - return priv->q + band; + return &priv->q[band]; } static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, struct sk_buff **to_free) { - if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) { - int band = prio2band[skb->priority & TC_PRIO_MAX]; - struct pfifo_fast_priv *priv = qdisc_priv(qdisc); - struct sk_buff_head *list = band2list(priv, band); - - priv->bitmap |= (1 << band); - qdisc->q.qlen++; - return __qdisc_enqueue_tail(skb, qdisc, list); - } + int band = prio2band[skb->priority & TC_PRIO_MAX]; + struct pfifo_fast_priv *priv = qdisc_priv(qdisc); + struct skb_array *q = band2list(priv, band); + int err; - return qdisc_drop(skb, qdisc, to_free); + err = skb_array_produce_bh(q, skb);
Do you need the _bh variant here? (Doesn't the qdisc run with BH disabled?)
+
+ if (unlikely(err))
+ return qdisc_drop_cpu(skb, qdisc, to_free);
+
+ qdisc_qstats_cpu_qlen_inc(qdisc);
+ qdisc_qstats_cpu_backlog_inc(qdisc, skb);
+ return NET_XMIT_SUCCESS;
}
static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
{
struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
- int band = bitmap2band[priv->bitmap];
+ struct sk_buff *skb = NULL;
+ int band;
- if (likely(band >= 0)) {
- struct sk_buff_head *list = band2list(priv, band);
- struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list);
+ for (band = 0; band < PFIFO_FAST_BANDS && !skb; band++) {
+ struct skb_array *q = band2list(priv, band);
- qdisc->q.qlen--;
- if (skb_queue_empty(list))
- priv->bitmap &= ~(1 << band);
+ if (__skb_array_empty(q))
+ continue;
- return skb;
+ skb = skb_array_consume_bh(q);Also _bh variant. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer