Over-running gc_thresh3

Peter Laws plaws at ou.edu
Fri Sep 4 15:14:10 UTC 2009

Simon Hobson wrote:

> While looking it up, I did come across this which makes for a good 
> read if you like details like that :
> http://book.chinaunix.net/special/ebook/oreilly/Understanding_Linux_Network_Internals/0596002556/understandlni-CHP-27-SECT-6.html

Well, I'm not sure I *like* details like that, but it was interesting to 
read.  The author, whom I hope was not the person that wrote that code, 
seems to assume that the only reason you'd ever exceed the default numbers 
is if you were running a Proxy ARP server.  I beg to differ (and I think 
you might, too!).

Anyway, yes, the change can be made on the fly (by echoing them into /proc) 
without anyone noticing and I did put them in /etc/sysctl.conf as well.

net.ipv4.neigh.default.gc_thresh3 = 4096
net.ipv4.neigh.default.gc_thresh2 = 2048
net.ipv4.neigh.default.gc_thresh1 = 1024

Have not had any overflows since.



Peter Laws / N5UWY
National Weather Center / Network Operations Center
University of Oklahoma Information Technology
plaws at ou.edu
Feedback? Contact my director, Craig Cochell, craigc at ou.edu. Thank you!

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