From: Jonathan Morton <chromatix99@gmail.com>
To: Justin Kilpatrick <justin@althea.net>
Cc: cake@lists.bufferbloat.net
Subject: Re: [Cake] Fighting bloat in the face of uncertinty
Date: Sun, 8 Sep 2019 02:42:34 +0300 [thread overview]
Message-ID: <E0C914DE-893D-4B14-9179-F10EB595DE0C@gmail.com> (raw)
In-Reply-To: <18b1c174-b88d-4664-9aa8-9c42925fc14c@www.fastmail.com>
> On 8 Sep, 2019, at 2:31 am, Justin Kilpatrick <justin@althea.net> wrote:
>
> If I set a throughput that's 50% too high should it still help? In my testing it didn't seem to.
In that case you would be relying on backpressure from the network interface to cause queuing to actually occur in Cake rather than in the driver or hardware (which would almost certainly be a dumb FIFO). If the driver doesn't implement BQL, that would easily explain 300ms of bloat.
In fact I'm unsure as to why changing the AQM parameters would cure it. You may have benefited from an unintentional second-order effect which we normally try to eliminate, when the 'target' parameter gets too close to the CPU scheduling latency of the kernel.
I generally find it's better to *underestimate* the bandwidth parameter by 50% than the reverse, simply to keep the queue out of the dumb hardware. But if you want to try implementing BQL in the relevant drivers, go ahead.
- Jonathan Morton
next prev parent reply other threads:[~2019-09-07 23:42 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-07 22:42 Justin Kilpatrick
2019-09-07 23:09 ` Jonathan Morton
2019-09-07 23:31 ` Justin Kilpatrick
2019-09-07 23:42 ` Jonathan Morton [this message]
2019-09-08 0:03 ` Justin Kilpatrick
2019-09-08 0:59 ` Jonathan Morton
2019-09-08 14:29 ` Justin Kilpatrick
2019-09-08 17:27 ` Jonathan Morton
2019-09-16 10:21 ` [Cake] cake memory consumption Sebastian Gottschall
2019-09-16 12:00 ` Dave Taht
2019-09-16 12:51 ` Dave Taht
2019-09-16 13:31 ` Sebastian Gottschall
2019-09-16 13:22 ` Sebastian Gottschall
2019-09-16 13:28 ` Justin Kilpatrick
2019-09-16 13:39 ` Jonathan Morton
2019-09-16 13:54 ` Sebastian Gottschall
2019-09-16 14:06 ` Jonathan Morton
2019-09-17 5:10 ` Sebastian Gottschall
2019-09-16 13:47 ` Sebastian Gottschall
2019-09-16 12:08 ` Toke Høiland-Jørgensen
2019-09-16 13:25 ` Sebastian Gottschall
2019-09-16 14:01 ` Toke Høiland-Jørgensen
2019-09-17 5:06 ` Sebastian Gottschall
2019-09-17 5:21 ` Sebastian Gottschall
2019-09-17 5:31 ` Sebastian Gottschall
2019-09-17 9:21 ` Jonathan Morton
2019-09-17 9:55 ` Sebastian Gottschall
2019-09-17 5:33 ` Sebastian Gottschall
2019-09-17 9:40 ` Toke Høiland-Jørgensen
2019-09-18 7:19 ` Sebastian Gottschall
2019-09-18 9:53 ` Toke Høiland-Jørgensen
2019-09-18 9:57 ` Sebastian Gottschall
2019-09-18 10:22 ` Toke Høiland-Jørgensen
2019-10-03 17:52 ` [Cake] Fighting bloat in the face of uncertinty Justin Kilpatrick
2019-10-03 18:41 ` Dave Taht
2019-10-03 19:04 ` Jonathan Morton
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