From: Eric Dumazet <edumazet@google.com>
Date: Wed, 13 Sep 2017 11:16:45 -0700
Subject: net_sched: gen_estimator: fix scaling error in bytes/packets samples
Patch-mainline: v4.14-rc1
Git-commit: ca558e185972d8ecd308760abf972f5d408bcff0
References: bsc1056787
Denys reported wrong rate estimations with HTB classes.
It appears the bug was added in linux-4.10, since my tests
where using intervals of one second only.
HTB using 4 sec default rate estimators, reported rates
were 4x higher.
We need to properly scale the bytes/packets samples before
integrating them in EWMA.
Tested:
echo 1 >/sys/module/sch_htb/parameters/htb_rate_est
Setup HTB with one class with a rate/cail of 5Gbit
Generate traffic on this class
tc -s -d cl sh dev eth0 classid 7002:11
class htb 7002:11 parent 7002:1 prio 5 quantum 200000 rate 5Gbit ceil
5Gbit linklayer ethernet burst 80000b/1 mpu 0b cburst 80000b/1 mpu 0b
level 0 rate_handle 1
Sent 1488215421648 bytes 982969243 pkt (dropped 0, overlimits 0
requeues 0)
rate 5Gbit 412814pps backlog 136260b 2p requeues 0
TCP pkts/rtx 982969327/45 bytes 1488215557414/68130
lended: 22732826 borrowed: 0 giants: 0
tokens: -1684 ctokens: -1684
Fixes: 1c0d32fde5bd ("net_sched: gen_estimator: complete rewrite of rate estimators")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Denys Fedoryshchenko <nuclearcat@nuclearcat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/core/gen_estimator.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -83,10 +83,10 @@ static void est_timer(unsigned long arg)
u64 rate, brate;
est_fetch_counters(est, &b);
- brate = (b.bytes - est->last_bytes) << (8 - est->ewma_log);
+ brate = (b.bytes - est->last_bytes) << (10 - est->ewma_log - est->intvl_log);
brate -= (est->avbps >> est->ewma_log);
- rate = (u64)(b.packets - est->last_packets) << (8 - est->ewma_log);
+ rate = (u64)(b.packets - est->last_packets) << (10 - est->ewma_log - est->intvl_log);
rate -= (est->avpps >> est->ewma_log);
write_seqcount_begin(&est->seq);