From: Stephen Hemminger <shemminger@linux-foundation.org>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: [PATCH 4/5] netem: avoid excessive requeues
Date: Wed, 21 Mar 2007 10:42:35 -0700 [thread overview]
Message-ID: <20070321174422.767901837@linux-foundation.org> (raw)
In-Reply-To: 20070321174231.890361963@linux-foundation.org
[-- Attachment #1: netem-throttle-opt.patch --]
[-- Type: text/plain, Size: 2339 bytes --]
The netem code would call getnstimeofday() and dequeue/requeue after
every packet, even if it was waiting. Avoid this overhead by using
the throttled flag.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
---
net/sched/sch_api.c | 3 +++
net/sched/sch_netem.c | 21 ++++++++++++---------
2 files changed, 15 insertions(+), 9 deletions(-)
--- net-2.6.22.orig/net/sched/sch_api.c
+++ net-2.6.22/net/sched/sch_api.c
@@ -298,6 +298,7 @@ static enum hrtimer_restart qdisc_watchd
timer);
wd->qdisc->flags &= ~TCQ_F_THROTTLED;
+ smp_wmb();
netif_schedule(wd->qdisc->dev);
return HRTIMER_NORESTART;
}
@@ -315,6 +316,7 @@ void qdisc_watchdog_schedule(struct qdis
ktime_t time;
wd->qdisc->flags |= TCQ_F_THROTTLED;
+ smp_wmb();
time = ktime_set(0, 0);
time = ktime_add_ns(time, PSCHED_US2NS(expires));
hrtimer_start(&wd->timer, time, HRTIMER_MODE_ABS);
@@ -325,6 +327,7 @@ void qdisc_watchdog_cancel(struct qdisc_
{
hrtimer_cancel(&wd->timer);
wd->qdisc->flags &= ~TCQ_F_THROTTLED;
+ smp_wmb();
}
EXPORT_SYMBOL(qdisc_watchdog_cancel);
--- net-2.6.22.orig/net/sched/sch_netem.c
+++ net-2.6.22/net/sched/sch_netem.c
@@ -272,6 +272,10 @@ static struct sk_buff *netem_dequeue(str
struct netem_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;
+ smp_mb();
+ if (sch->flags & TCQ_F_THROTTLED)
+ return NULL;
+
skb = q->qdisc->dequeue(q->qdisc);
if (skb) {
const struct netem_skb_cb *cb
@@ -284,18 +288,17 @@ static struct sk_buff *netem_dequeue(str
if (PSCHED_TLESS(cb->time_to_send, now)) {
pr_debug("netem_dequeue: return skb=%p\n", skb);
sch->q.qlen--;
- sch->flags &= ~TCQ_F_THROTTLED;
return skb;
- } else {
- qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
+ }
- if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
- qdisc_tree_decrease_qlen(q->qdisc, 1);
- sch->qstats.drops++;
- printk(KERN_ERR "netem: queue discpline %s could not requeue\n",
- q->qdisc->ops->id);
- }
+ if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) {
+ qdisc_tree_decrease_qlen(q->qdisc, 1);
+ sch->qstats.drops++;
+ printk(KERN_ERR "netem: %s could not requeue\n",
+ q->qdisc->ops->id);
}
+
+ qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
}
return NULL;
--
next prev parent reply other threads:[~2007-03-21 17:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-21 17:42 [PATCH 0/5] netem performance improvements Stephen Hemminger
2007-03-21 17:42 ` [PATCH 1/5] netem: report reorder percent correctly Stephen Hemminger
2007-03-21 17:42 ` [PATCH 2/5] netem: use better types for time values Stephen Hemminger
2007-03-21 17:42 ` [PATCH 3/5] netem: optimize tfifo Stephen Hemminger
2007-03-21 17:42 ` Stephen Hemminger [this message]
2007-03-22 20:40 ` [PATCH 4/5] netem: avoid excessive requeues Patrick McHardy
2007-03-22 21:08 ` David Miller
2007-03-23 11:06 ` Patrick McHardy
2007-03-23 13:26 ` Patrick McHardy
2007-03-21 17:42 ` [PATCH 5/5] qdisc: avoid transmit softirq on watchdog wakeup Stephen Hemminger
2007-03-22 19:19 ` [PATCH 0/5] netem performance improvements David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20070321174422.767901837@linux-foundation.org \
--to=shemminger@linux-foundation.org \
--cc=davem@davemloft.net \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.