Re: non-standard TCP tunings in EC2 images

[Thomas Goirand <zigo@debian.org>]

On 07/20/2016 08:59 AM, Lucas Nussbaum wrote:
> - there's a number of sysctl changes in /etc/sysctl.d/01_ec2.conf:
>     vm.swappiness = 0
>     vm.dirty_ratio = 80
>     vm.dirty_background_ratio = 5
>     vm.dirty_expire_centisecs = 12000
>     net.core.somaxconn = 1000
>     net.core.netdev_max_backlog = 5000
>     net.core.rmem_max = 16777216
>     net.core.wmem_max = 16777216
>     net.ipv4.tcp_wmem = 4096 12582912 16777216
>     net.ipv4.tcp_rmem = 4096 12582912 16777216
>     net.ipv4.tcp_max_syn_backlog = 8096
>     net.ipv4.tcp_slow_start_after_idle = 0
>     net.ipv4.tcp_tw_reuse = 1
>     net.ipv4.ip_local_port_range = 10240 65535
>     kernel.sysrq = 0

Look here:
https://www.youtube.com/watch?v=7Cyd22kOqWc

at 28:58 and 30:50

That's crazy. What Netflix presented as what seems to be custom tuning
parameters specific *for they application* has been copy/past directly
into the Debian EC2 "official" image, without any reasoning. It may be
very good for Netflix, but very bad for the general purpose: the
presentation doesn't explain this very much.

We call this image "official". I'm not amused. :/

Cheers,

Thomas Goirand (zigo)