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edb09eb17e
Large tc dumps (tc -s {qdisc|class} sh dev ethX) done by Google BwE host
agent [1] are problematic at scale :
For each qdisc/class found in the dump, we currently lock the root qdisc
spinlock in order to get stats. Sampling stats every 5 seconds from
thousands of HTB classes is a challenge when the root qdisc spinlock is
under high pressure. Not only the dumps take time, they also slow
down the fast path (queue/dequeue packets) by 10 % to 20 % in some cases.
An audit of existing qdiscs showed that sch_fq_codel is the only qdisc
that might need the qdisc lock in fq_codel_dump_stats() and
fq_codel_dump_class_stats()
In v2 of this patch, I now use the Qdisc running seqcount to provide
consistent reads of packets/bytes counters, regardless of 32/64 bit arches.
I also changed rate estimators to use the same infrastructure
so that they no longer need to lock root qdisc lock.
[1]
http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43838.pdf
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Kevin Athey <kda@google.com>
Cc: Xiaotian Pei <xiaotian@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
69 lines
2.3 KiB
C
69 lines
2.3 KiB
C
#ifndef __NET_GEN_STATS_H
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#define __NET_GEN_STATS_H
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#include <linux/gen_stats.h>
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#include <linux/socket.h>
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#include <linux/rtnetlink.h>
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#include <linux/pkt_sched.h>
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struct gnet_stats_basic_cpu {
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struct gnet_stats_basic_packed bstats;
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struct u64_stats_sync syncp;
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};
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struct gnet_dump {
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spinlock_t * lock;
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struct sk_buff * skb;
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struct nlattr * tail;
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/* Backward compatibility */
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int compat_tc_stats;
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int compat_xstats;
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int padattr;
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void * xstats;
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int xstats_len;
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struct tc_stats tc_stats;
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};
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int gnet_stats_start_copy(struct sk_buff *skb, int type, spinlock_t *lock,
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struct gnet_dump *d, int padattr);
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int gnet_stats_start_copy_compat(struct sk_buff *skb, int type,
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int tc_stats_type, int xstats_type,
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spinlock_t *lock, struct gnet_dump *d,
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int padattr);
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int gnet_stats_copy_basic(const seqcount_t *running,
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struct gnet_dump *d,
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struct gnet_stats_basic_cpu __percpu *cpu,
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struct gnet_stats_basic_packed *b);
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void __gnet_stats_copy_basic(const seqcount_t *running,
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struct gnet_stats_basic_packed *bstats,
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struct gnet_stats_basic_cpu __percpu *cpu,
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struct gnet_stats_basic_packed *b);
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int gnet_stats_copy_rate_est(struct gnet_dump *d,
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const struct gnet_stats_basic_packed *b,
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struct gnet_stats_rate_est64 *r);
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int gnet_stats_copy_queue(struct gnet_dump *d,
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struct gnet_stats_queue __percpu *cpu_q,
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struct gnet_stats_queue *q, __u32 qlen);
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int gnet_stats_copy_app(struct gnet_dump *d, void *st, int len);
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int gnet_stats_finish_copy(struct gnet_dump *d);
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int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
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struct gnet_stats_basic_cpu __percpu *cpu_bstats,
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struct gnet_stats_rate_est64 *rate_est,
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spinlock_t *stats_lock,
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seqcount_t *running, struct nlattr *opt);
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void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
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struct gnet_stats_rate_est64 *rate_est);
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int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
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struct gnet_stats_basic_cpu __percpu *cpu_bstats,
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struct gnet_stats_rate_est64 *rate_est,
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spinlock_t *stats_lock,
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seqcount_t *running, struct nlattr *opt);
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bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
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const struct gnet_stats_rate_est64 *rate_est);
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#endif
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