Device polling

Jon Noack noackjr at
Sun Jun 13 21:07:30 GMT 2004

On 06/13/04 13:13, Ruslan Ermilov wrote:
> On Sun, Jun 13, 2004 at 01:07:28PM -0500, Jon Noack wrote:
>> I just tested this on my SMP all-in-one home server (Web, Mail,
>> NFS, Samba, Squid, etc.).  It's been up for over 24 hours with no
>> apparent issues.  The machine is used pretty heavily, with NFS
>> mounted home directories and CVS mirror (see below) -- a CVS update
>> of the src tree over NFS has done a good job of breaking fragile
>> setups in the past. Everything seemed OK.  That said, peak
>> performance (as tested by iperf) took a nosedive: with 32-bit em
>> adapters (gige), tcp bandwidth dropped from over 360Mbps to around
>> 200 Mbps.  If anyone has any suggestions for more in-depth testing,
>> I'd be willing to try them.  If I have the time I may also try the
>> latest netperf patch and see how that affects things.
> What are your operational polling(4) parameters?  What the HZ is set
> to?

HZ=1000 and I was using the defaults for polling.  Bumping up burst_max 
to 300 results in slightly better peak performance at 220 Mbps. 
polling(4) says burst_max=150 is good for HZ=1000 and 100 Mbit networks; 
are there any recommendations (for burst_max or in general) for 1 Gbit 

$ sysctl kern.polling
kern.polling.burst: 150
kern.polling.each_burst: 5
kern.polling.burst_max: 150
kern.polling.idle_poll: 0
kern.polling.poll_in_trap: 0
kern.polling.user_frac: 50
kern.polling.reg_frac: 20
kern.polling.short_ticks: 2000
kern.polling.lost_polls: 403164
kern.polling.pending_polls: 0
kern.polling.residual_burst: 0
kern.polling.handlers: 1
kern.polling.enable: 1
kern.polling.phase: 0
kern.polling.suspect: 365727
kern.polling.stalled: 0
kern.polling.idlepoll_sleeping: 1


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