xl(4) & polling
subhro.kar at gmail.com
Wed May 11 08:11:34 PDT 2005
On 5/11/2005 13:57, Tuomo Latto wrote:
> Subhro wrote:
>> In Device Polled systems, the NIC does not generate any interrupt at
>> all. Instead whenever the packets arrive at a Network interface, they
>> are captured and put into a queue. The kernel scheduler checks the
>> quese at regular intervals and processes the packets which are
>> waiting. This interval is adjusted by the "options HZ=x" kernel option.
>> If the value of x is very high, there may eb two scenarios. In the
>> first scenario, the queue may fill up and subsequent packets are
>> dropped. In this case retransmission of the packets are required. In
>> the second scenario, the packets would be held up for excessive long
>> times which defeats the entire purpose of Device Polling. If the
>> value of x is very low, the scheduler would check the queue
>> frequently and would again defeat the entire idea of Device Polling.
> It's the other way around. Large values indicate larger polling frequency
> thus amounting to more checks. Or at least the name of the option would
> suggest that anyway.
Silly me :(. I meant something, typed something else. Its indeed the
other way round. Thanks to everyone who pointed this out.
More information about the freebsd-stable