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From: Adrian Popescu <adriannnpopescu@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@toke.dk>
Cc: cake@lists.bufferbloat.net
Subject: Re: [Cake] Cake3 - source code and some questions
Date: Thu, 23 Apr 2015 14:05:27 +0300	[thread overview]
Message-ID: <CAF3M4P3=vicGAp+YZSvFzRBvBkRKh8iQb15F+3gYUyo+og3n=g@mail.gmail.com> (raw)
In-Reply-To: <87lhhj85xs.fsf@toke.dk>

The problems I was seeing were related to c-states.

PCI-E bus ASPM power saving is disabled for the e1000e network
interfaces. This can be observed using dmesg.

Perhaps using a CPU which is low power enough for a router would help
avoid the need of deep sleep power states and other things such as
speedstep.


On Thu, Apr 23, 2015 at 2:01 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> Adrian Popescu <adriannnpopescu@gmail.com> writes:
>
>> Thanks to your experiment and your statement regarding CPU load on
>> your box during testing, I was able to fix the problem.
>
> Cool!
>
>> It looks like this problem was being caused by power saving. Something
>> changed between the older kernels and the newer ones. Changing the
>> power saving settings in the BIOS brings back latency below 0.5
>> milliseconds.
>
> So is this the PCI bus power saving settings, or the CPU, or?
>
>> This might have an impact some benchmarks which don't load up all CPU
>> cores or which don't need a lot of CPU power. This is certainly
>> something to keep an eye on when doing any kind of testing involving
>> really low latencies or network schedulers.
>
> Yes, definitely. Having things be worse during idle is definitely not
> optimal. I wonder if there's a kernel-level setting that can affect this?
>
> -Toke

  reply	other threads:[~2015-04-23 11:05 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-12  9:39 Adrian Popescu
2015-04-12  9:58 ` Jonathan Morton
2015-04-12 10:24 ` Jonathan Morton
2015-04-12 12:33   ` Adrian Popescu
2015-04-12 18:57     ` Jonathan Morton
2015-04-16 12:14       ` Adrian Popescu
2015-04-16 13:25         ` Jonathan Morton
2015-04-16 13:48           ` Adrian Popescu
2015-04-16 19:26             ` Dave Taht
2015-04-22 21:02               ` Adrian Popescu
2015-04-23  0:45                 ` Stephen Hemminger
2015-04-23  9:01                 ` Toke Høiland-Jørgensen
2015-04-23 10:56                   ` Adrian Popescu
2015-04-23 11:01                     ` Toke Høiland-Jørgensen
2015-04-23 11:05                       ` Adrian Popescu [this message]
2015-04-23 11:09                         ` Toke Høiland-Jørgensen
2015-04-23 11:13                           ` Jonathan Morton
2015-04-16 13:49           ` Sebastian Moeller

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