linux/include/net/gen_stats.h
Eric Dumazet edb09eb17e net: sched: do not acquire qdisc spinlock in qdisc/class stats dump
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>
2016-06-07 16:37:14 -07:00

69 lines
2.3 KiB
C

#ifndef __NET_GEN_STATS_H
#define __NET_GEN_STATS_H
#include <linux/gen_stats.h>
#include <linux/socket.h>
#include <linux/rtnetlink.h>
#include <linux/pkt_sched.h>
struct gnet_stats_basic_cpu {
struct gnet_stats_basic_packed bstats;
struct u64_stats_sync syncp;
};
struct gnet_dump {
spinlock_t * lock;
struct sk_buff * skb;
struct nlattr * tail;
/* Backward compatibility */
int compat_tc_stats;
int compat_xstats;
int padattr;
void * xstats;
int xstats_len;
struct tc_stats tc_stats;
};
int gnet_stats_start_copy(struct sk_buff *skb, int type, spinlock_t *lock,
struct gnet_dump *d, int padattr);
int gnet_stats_start_copy_compat(struct sk_buff *skb, int type,
int tc_stats_type, int xstats_type,
spinlock_t *lock, struct gnet_dump *d,
int padattr);
int gnet_stats_copy_basic(const seqcount_t *running,
struct gnet_dump *d,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b);
void __gnet_stats_copy_basic(const seqcount_t *running,
struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b);
int gnet_stats_copy_rate_est(struct gnet_dump *d,
const struct gnet_stats_basic_packed *b,
struct gnet_stats_rate_est64 *r);
int gnet_stats_copy_queue(struct gnet_dump *d,
struct gnet_stats_queue __percpu *cpu_q,
struct gnet_stats_queue *q, __u32 qlen);
int gnet_stats_copy_app(struct gnet_dump *d, void *st, int len);
int gnet_stats_finish_copy(struct gnet_dump *d);
int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
seqcount_t *running, struct nlattr *opt);
void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_rate_est64 *rate_est);
int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
seqcount_t *running, struct nlattr *opt);
bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
const struct gnet_stats_rate_est64 *rate_est);
#endif