[Cerowrt-devel] fq_codel tuning on distros

Matt Taggart matt at lackof.org
Fri Oct 17 17:06:41 EDT 2014


Hi,

http://www.bufferbloat.net/projects/codel/wiki/Best_practices_for_benchmarki
ng_Codel_and_FQ_Codel#Tuning-fq_codel

explains that the default packet limit of 10000 is designed for 10GigE 
speeds and that for slower links it should be turned down. Is that still 
true? Looking at 3.16 source in fq_codel_init I see:

  sch->limit = 10*1024;
  q->flows_cnt = 1024;

But I don't know what those correspond to. Are they sysfs tunable or only 
at compile time?
If Linux distros are going to turn on fq_codel by default, are these 
reasonable values for the installed base (which I am assuming is mostly 
1GigE)? What recommendations should the distro documentation make for 
tuning on various speeds?

I'm excited for this to go into distros, what needs to be done to make that 
easier?

Thanks,

-- 
Matt Taggart
matt at lackof.org





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