forked from luck/tmp_suning_uos_patched
a9efad8b24
I found a serious performance bug in packet schedulers using hrtimers.
sch_htb and sch_fq are definitely impacted by this problem.
We constantly rearm high resolution timers if some packets are throttled
in one (or more) class, and other packets are flying through qdisc on
another (non throttled) class.
hrtimer_start() does not have the mod_timer() trick of doing nothing if
expires value does not change :
if (timer_pending(timer) &&
timer->expires == expires)
return 1;
This issue is particularly visible when multiple cpus can queue/dequeue
packets on the same qdisc, as hrtimer code has to lock a remote base.
I used following fix :
1) Change htb to use qdisc_watchdog_schedule_ns() instead of open-coding
it.
2) Cache watchdog prior expiration. hrtimer might provide this, but I
prefer to not rely on some hrtimer internal.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
137 lines
3.8 KiB
C
137 lines
3.8 KiB
C
#ifndef __NET_PKT_SCHED_H
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#define __NET_PKT_SCHED_H
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#include <linux/jiffies.h>
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#include <linux/ktime.h>
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#include <linux/if_vlan.h>
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#include <net/sch_generic.h>
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struct qdisc_walker {
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int stop;
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int skip;
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int count;
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int (*fn)(struct Qdisc *, unsigned long cl, struct qdisc_walker *);
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};
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#define QDISC_ALIGNTO 64
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#define QDISC_ALIGN(len) (((len) + QDISC_ALIGNTO-1) & ~(QDISC_ALIGNTO-1))
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static inline void *qdisc_priv(struct Qdisc *q)
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{
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return (char *) q + QDISC_ALIGN(sizeof(struct Qdisc));
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}
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/*
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Timer resolution MUST BE < 10% of min_schedulable_packet_size/bandwidth
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Normal IP packet size ~ 512byte, hence:
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0.5Kbyte/1Mbyte/sec = 0.5msec, so that we need 50usec timer for
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10Mbit ethernet.
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10msec resolution -> <50Kbit/sec.
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The result: [34]86 is not good choice for QoS router :-(
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The things are not so bad, because we may use artificial
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clock evaluated by integration of network data flow
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in the most critical places.
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*/
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typedef u64 psched_time_t;
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typedef long psched_tdiff_t;
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/* Avoid doing 64 bit divide */
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#define PSCHED_SHIFT 6
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#define PSCHED_TICKS2NS(x) ((s64)(x) << PSCHED_SHIFT)
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#define PSCHED_NS2TICKS(x) ((x) >> PSCHED_SHIFT)
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#define PSCHED_TICKS_PER_SEC PSCHED_NS2TICKS(NSEC_PER_SEC)
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#define PSCHED_PASTPERFECT 0
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static inline psched_time_t psched_get_time(void)
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{
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return PSCHED_NS2TICKS(ktime_get_ns());
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}
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static inline psched_tdiff_t
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psched_tdiff_bounded(psched_time_t tv1, psched_time_t tv2, psched_time_t bound)
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{
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return min(tv1 - tv2, bound);
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}
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struct qdisc_watchdog {
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u64 last_expires;
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struct hrtimer timer;
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struct Qdisc *qdisc;
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};
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void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
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void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires, bool throttle);
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static inline void qdisc_watchdog_schedule(struct qdisc_watchdog *wd,
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psched_time_t expires)
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{
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qdisc_watchdog_schedule_ns(wd, PSCHED_TICKS2NS(expires), true);
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}
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void qdisc_watchdog_cancel(struct qdisc_watchdog *wd);
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extern struct Qdisc_ops pfifo_qdisc_ops;
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extern struct Qdisc_ops bfifo_qdisc_ops;
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extern struct Qdisc_ops pfifo_head_drop_qdisc_ops;
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int fifo_set_limit(struct Qdisc *q, unsigned int limit);
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struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
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unsigned int limit);
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int register_qdisc(struct Qdisc_ops *qops);
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int unregister_qdisc(struct Qdisc_ops *qops);
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void qdisc_get_default(char *id, size_t len);
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int qdisc_set_default(const char *id);
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void qdisc_list_add(struct Qdisc *q);
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void qdisc_list_del(struct Qdisc *q);
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struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
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struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);
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struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
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struct nlattr *tab);
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void qdisc_put_rtab(struct qdisc_rate_table *tab);
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void qdisc_put_stab(struct qdisc_size_table *tab);
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void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc);
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int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
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struct net_device *dev, struct netdev_queue *txq,
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spinlock_t *root_lock, bool validate);
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void __qdisc_run(struct Qdisc *q);
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static inline void qdisc_run(struct Qdisc *q)
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{
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if (qdisc_run_begin(q))
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__qdisc_run(q);
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}
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int tc_classify(struct sk_buff *skb, const struct tcf_proto *tp,
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struct tcf_result *res, bool compat_mode);
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static inline __be16 tc_skb_protocol(const struct sk_buff *skb)
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{
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/* We need to take extra care in case the skb came via
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* vlan accelerated path. In that case, use skb->vlan_proto
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* as the original vlan header was already stripped.
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*/
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if (skb_vlan_tag_present(skb))
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return skb->vlan_proto;
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return skb->protocol;
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}
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/* Calculate maximal size of packet seen by hard_start_xmit
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routine of this device.
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*/
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static inline unsigned int psched_mtu(const struct net_device *dev)
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{
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return dev->mtu + dev->hard_header_len;
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}
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#endif
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