On 08/01/11 12:41, Camaleón wrote:
On Sat, 08 Jan 2011 11:16:39 +0000, Alan Chandler wrote:
After a Slashdot entry, I discovered an interesting series of blog posts
by Jim Gettys. The series starts
http://gettys.wordpress.com/2010/10/02/first-puzzle-piece/ (unlike
Slashdot which linked to a random place in the middle).
...
How to set txqueuelen?
http://www.debian-administration.org/users/ajt/weblog/188
Question is why should we manually tweak that value at all? Are the
defaults bad/incorrectly set or are they very conservative? What is the
gain to increasing it? Will it have any drawbacks? What happens with
"bonded" interfaces (mode 1 or mode 3)? :-?
If you read Jim's blog articles, he basically argues that the built in
TCP congestion control mechanisms are blunted because there is a delay
in noticing congestion build up as the buffers fill up. The effect is
that on congested links, latency and jitter can become very high
(several seconds).
With memory so cheap these days, the tendancy has been to increase
available buffering to the point where there is far too much of it. This
means that the problem of jitter and latency has got worse
He is suggesting that since most ethernet chips have internal ring
buffers that txqueuelen should be set to 0.
I must admit I notice sometimes at home when playing youtube videos - it
has all been running smoothly for a while and then suddenly you get into
buffering mode over and over again.
I thought I might experiment with setting txqueuelen to 0 to see what
difference it made.
--
Alan Chandler
http://www.chandlerfamily.org.uk
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