[Click] question about linuxmodule/fromdevice

[Eddie Kohler]

Hi Mythili,

(1) You should probably be using a more current version of Click 
(git/cvs) -- as should anyone :)

(2) Click's interrupt-based network path, which is what you are using 
with FromDevice, is NOT designed for speed or low latency.  It is 
designed for simplicity and correctness.  If you need low latency, you 
can either go the route suggested by Roman Chertov and change the device 
driver yourself, or (perhaps easier) use Click in polling mode with 
PollDevice.  The polling path is much lower latency.  However, polling 
mode only works for certain network cards, including Intel e1000.

Eddie


Mythili Vutukuru wrote:
> Hi,
> I am running click version 1.5.0. The application I am building requires
> that the delay between the network interface receiving the packet and my
> custom click element processing the packet be minimum. Currently, the
> FromDevice element queues up packets at interrupt time, and pushes them
> out of its output when the task in the element is scheduled. I want to
> reduce this delay. First question: is there any obvious way to do this?
> I tried increasing the tickets of FromDevice using ScheduleInfo, but it
> did not help.
> 
> An obvious (but possibly flawed) approach I thought of is the following:
> make FromDevice push out the packets at interrupt time itself to other
> elements downstream. Second question: does running some click element
> code at interrupt time break anything fundamental in the click
> architecture?
> 
> Thanks a lot, any help is much appreciated.
> 
> Mythili
> 
> 
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