Re: Using Unix TC to shape high bandwidth traffic

[Andy Furniss <adf.lists@gmail.com>]

LAMBRUSCHI Yannick (EXT) wrote:
> Hello,
>
>
> Thanks for the post. We also played with mtu 1514 (and even greater)
> but did not change anything. I really think it comes from the jiffy
> limit but can't find another way..

Strangely I have now tested with your command and mtu 1514 and I can get
gig speed OK.

I was thinking possibly you could just omit the peak rate and mtu (which
seems to be another buffer size) and see if it was OK.

I don't know why I am not limited like you but -

I am using tcp netperf.

My mobo gig nic is dumb so doesn't offload. I guess a 10 gig nic will
offload, so unless you already turned it off with ethtool it's possible
the kernel is sending huge packets to the nic.

Maybe try far bigger mtu or not bother with peakrate/mtu - FWIW setting
1000mbit peakrate is still going to be faster than a gig nic can go as
there are overheads above what tc sees.

It could be kernel settings - you mention jiffies, tbf is ancient and I
don't know whether it was ever changed, or if kernel settings can change
things.

I don't know why I am not limited like you grepping hz from my config
looks like -

ph4[1080i25]$ grep -i hz /boot/config-4.2.0-rc4-g194a336
CONFIG_HZ_PERIODIC=y
# CONFIG_NO_HZ_IDLE is not set
# CONFIG_NO_HZ_FULL is not set
# CONFIG_NO_HZ is not set
# CONFIG_HZ_100 is not set
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
CONFIG_HZ_1000=y
CONFIG_HZ\x1000
# CONFIG_MACHZ_WDT is not set