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From: Eric Dumazet <eric.dumazet@gmail.com>
To: netdev <netdev@vger.kernel.org>
Cc: Alexander Duyck <aduyck@mirantis.com>
Subject: [RFC] net: remove busylock
Date: Thu, 19 May 2016 10:08:36 -0700	[thread overview]
Message-ID: <1463677716.18194.203.camel@edumazet-glaptop3.roam.corp.google.com> (raw)

busylock was added at the time we had expensive ticket spinlocks

(commit 79640a4ca6955e3ebdb7038508fa7a0cd7fa5527 ("net: add additional
lock to qdisc to increase throughput")

Now kernel spinlocks are MCS, this busylock things is no longer
relevant. It is slowing down things a bit.


With HTB qdisc, here are the numbers for 200 concurrent TCP_RR, on a host with 48 hyperthreads.

lpaa5:~# sar -n DEV 4 4 |grep eth0
10:05:44         eth0 798951.25 798951.75  52276.22  52275.26      0.00      0.00      0.50
10:05:48         eth0 798576.00 798572.75  52251.24  52250.39      0.00      0.00      0.75
10:05:52         eth0 798746.00 798748.75  52262.89  52262.13      0.00      0.00      0.50
10:05:56         eth0 798303.25 798291.50  52235.22  52233.10      0.00      0.00      0.50
Average:         eth0 798644.12 798641.19  52256.39  52255.22      0.00      0.00      0.56

Disabling busylock (by using a local sysctl)

lpaa5:~# sar -n DEV 4 4 |grep eth0
10:05:14         eth0 864085.75 864091.50  56538.09  56537.46      0.00      0.00      0.50
10:05:18         eth0 864734.75 864729.25  56580.35  56579.05      0.00      0.00      0.75
10:05:22         eth0 864366.00 864361.50  56556.74  56555.00      0.00      0.00      0.50
10:05:26         eth0 864246.50 864248.75  56549.19  56547.65      0.00      0.00      0.50
Average:         eth0 864358.25 864357.75  56556.09  56554.79      0.00      0.00      0.56

That would be a 8 % increase.

             reply	other threads:[~2016-05-19 17:08 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-19 17:08 Eric Dumazet [this message]
2016-05-19 18:03 ` [RFC] net: remove busylock Alexander Duyck
2016-05-19 18:41   ` Rick Jones
2016-05-19 18:56   ` Eric Dumazet
2016-05-19 19:35     ` Eric Dumazet
2016-05-19 20:39       ` Alexander Duyck
2016-05-20  4:49         ` John Fastabend
2016-05-20  4:56           ` Eric Dumazet
2016-05-20  7:29   ` Jesper Dangaard Brouer
2016-05-20 13:11     ` Eric Dumazet
2016-05-20 13:47       ` Eric Dumazet
2016-05-20 14:16         ` Eric Dumazet
2016-05-20 17:49           ` Jesper Dangaard Brouer
2016-05-20 21:32             ` Eric Dumazet
2016-05-23  9:50               ` Jesper Dangaard Brouer
2016-05-23 21:24                 ` [PATCH net] net_sched: avoid too many hrtimer_start() calls Eric Dumazet
2016-05-24 21:49                   ` David Miller
2016-05-24 13:50             ` [RFC] net: remove busylock David Laight
2016-05-24 14:37               ` Eric Dumazet
2016-05-20 16:01       ` John Fastabend
2016-05-19 18:12 ` David Miller
2016-05-19 18:44   ` Eric Dumazet

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