haesu at towardex.com
Wed Nov 17 21:03:22 GMT 2004
On Thu, Nov 18, 2004 at 01:52:49AM +0700, Eugene Grosbein wrote:
> On Wed, Nov 17, 2004 at 09:13:51PM +0300, Yar Tikhiy wrote:
> > The router box is a 1.4GHz Celeron PC with an fxp(4) interface split
> > across a dozen of vlans. There is nothing special about its setup
> > except for ~250 rules loaded into ipfw2. It is running 4.10-RELEASE.
> > Without polling, it was able to switch full 10Mbytes/sec of traffic
> > (~9kpps), but that took from 50 to 70% CPU time spent in interrupts.
> > With polling on, interrupt time never exceeds 5% and it stays as low
> > as 1-2% on average even when traffic is that high.
> Does polling(4) increase latency? It is very imortant for router
> that handles lots of RTP (VoIP) traffic.
If you have a box doing lot of traffic in packets per second, enabling
polling with HZ=2000 +/- will actually *decrease* latency due to far
lower overhead instead of handling all those interrupts/sec.
On a low-to-no traffic box, it's probably not worth it, however use
your own judgement. Either way, the amount of latency polling(4) adds even
in HZ=100 is very low enough (1 ms or less. if using 2000 or so, there is
not much noticeable latency in line of microseconds) to affect most
James Jun TowardEX Technologies, Inc.
Technical Lead IPv4 and Native IPv6 Colocation, Bandwidth,
james at towardex.com and Web Hosting Services in the Metro Boston area
cell: 1(978)-394-2867 web: http://www.towardex.com , noc: www.twdx.net
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