linux-kernel - [PATCH 4.13 008/160] net_sched: gen_estimator: fix scaling error in bytes/packets samples

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Date:   Tue, 10 Oct 2017 21:48:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Denys Fedoryshchenko <nuclearcat@...learcat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.13 008/160] net_sched: gen_estimator: fix scaling error in bytes/packets samples

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>


[ Upstream commit ca558e185972d8ecd308760abf972f5d408bcff0 ]

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@...gle.com>
Reported-by: Denys Fedoryshchenko <nuclearcat@...learcat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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);