From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-x231.google.com (mail-qg0-x231.google.com [IPv6:2607:f8b0:400d:c04::231]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 18DF721F35C for ; Thu, 23 Apr 2015 03:56:43 -0700 (PDT) Received: by qgeb100 with SMTP id b100so6057870qge.3 for ; Thu, 23 Apr 2015 03:56:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=zhOCr3Wk/0HUW0qr5VSQ0qThNj/E3M59+NvnlAyozpQ=; b=wXMIC9Tjwv76iELhPGHcTJy9caewlWFhVv4DHSX6RrlLkz43C0F+cWmwQxigoqamrk bqEY57+9/GcD7TMVBuvLkk0YziCxUVtlwPOrdhIijS/o2ZU+p8jl7q1S3jt29Zv8vS3W u9YZA+Sv9+xDS7p0FVUAcHkicyC0ppnjrJnuvUMUo3gPB7jJapj5u6KwGLoNZPTOXCjG up5pArOnxroHn2pq+UxLzZvedU6oG5WxBOgfji3ToR5dBNvMKUtMgPQTM5pRgnfJfAYc 9BM/DGb2X4rg3XnzTsBbhapqCZ7gDkid6pPyLpBaA8DcE6ioq8cp6p02F0lkD0y3Q73N 3xJg== MIME-Version: 1.0 X-Received: by 10.55.48.16 with SMTP id w16mr3758841qkw.13.1429786602558; Thu, 23 Apr 2015 03:56:42 -0700 (PDT) Received: by 10.140.30.52 with HTTP; Thu, 23 Apr 2015 03:56:42 -0700 (PDT) In-Reply-To: <87383r9q1u.fsf@toke.dk> References: <5BC1CA30-289D-42B4-95CD-3AE5D7B96F09@gmail.com> <87383r9q1u.fsf@toke.dk> Date: Thu, 23 Apr 2015 13:56:42 +0300 Message-ID: From: Adrian Popescu To: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: cake@lists.bufferbloat.net Subject: Re: [Cake] Cake3 - source code and some questions X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Apr 2015 10:57:12 -0000 Hello Toke, Thanks to your experiment and your statement regarding CPU load on your box during testing, I was able to fix the problem. 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. 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. On Thu, Apr 23, 2015 at 12:01 PM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > Adrian Popescu writes: > >> Seeing worse latency under load (20-100 milliseconds) isn't uncommon. >> I believe this to be a regression in the kernel or in the network >> drivers. > > I don't see this behaviour at all: > > $ ls -l /sys/class/net/enp0s25/device/driver = = = :( > 0 lrwxrwxrwx 1 root root 0 Apr 21 16:05 /sys/class/net/enp0s25/device/dri= ver -> ../../../bus/pci/drivers/e1000e/ > > $ ping 130.243.26.1 -c 100 # this is my default gateway > ..snip... > --- 130.243.26.1 ping statistics --- > 100 packets transmitted, 100 received, 0% packet loss, time 99000ms > rtt min/avg/max/mdev =3D 0.341/0.801/28.260/2.769 ms > > $ cat /proc/loadavg > 9.29 8.43 5.30 14/508 6665 > > (yes, this is while running a cpu-hungry data processing application in > the background on all eight cores) > > $ uname -a > Linux alrua-kau 3.19.3-3-ARCH #1 SMP PREEMPT Wed Apr 8 14:10:00 CEST 2015= x86_64 GNU/Linux > > $ tc qdisc show dev enp0s25 > qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 = 1 1 1 1 1 > > (hmm, why am I running pfifo_fast?) > > Repeating with sch_fq: > > $ ping 130.243.26.1 -c 100 > ...snip... > --- 130.243.26.1 ping statistics --- > 100 packets transmitted, 100 received, 0% packet loss, time 98998ms > rtt min/avg/max/mdev =3D 0.358/0.468/1.278/0.151 ms > > -Toke