Experimental Physics and
Industrial Control System

Kyle Lanclos <[email protected]> · Wed, 5 Sep 2018 08:11:52 -1000

It's been a long time since I felt the need to do network tuning on a
Linux host. Back when I still felt that need (some 15+ years ago) I
attempted to tune my way to better throughput on a gigabit network;
everything I tried made the performance worse than the automatic
behavior in the stock Linux kernel.

I don't doubt that there are special cases where tuning matters. None
of my fairly aggressive cases were special enough to cross that
threshold. I wouldn't be surprised if these delays are somewhere
else-- have you confirmed your name resolution setup is correct?

--Kyle

On Wed, Sep 5, 2018 at 8:06 AM Eric Norum <[email protected]> wrote:
>
> Are there guidelines for tuning the network parameters for a Linux host running a bunch of EPICS soft IOCs?  We were seeing some issues with CA clients seeing delays of over a second for ‘get' requests.  Setting the values shown here:
>
> net.core.netdev_max_backlog = 5000
> net.core.rmem_max = 8388608
> net.core.wmem_max = 8388608
> net.core.rmem_default = 124928
> net.core.wmem_default = 124928
> net.ipv4.tcp_rmem = 4096 87380 8388608
> net.ipv4.tcp_wmem = 4096 65536 8388608
> net.ipv4.tcp_mem = 8388608 8388608 8388608
>
> seems to have improved things.  But I don’t know if those numbers, which I got from a google search, are way too big, or not yet big enough or completely weird.
> Suggestions welcomed.
>
> Machine details:
>
> 8 cores
> 24 GiB RAM
> 1 TB SSD
> Gigabit Ethernet
> EPICS R3.15.4
>
> Load average in the 3 to 4 range but CPU utilization as shown by ‘top’ showed at least 60% idle even when clients were experiencing the slow response.
>
>  --
> Eric Norum
> [email protected]
>
>
>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System