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
next prev parent 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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