How to set Linux Max Queue Length ?

Hi, folks,

Do you know how to increase the FIFO (both input and output) packet queue
limits (Default is 100 packets) to, say, 1000 packets ?

I mean, where is the file that defines this default limit ?

Also, this seems to be the protocol independent queue. I want to increase
all possible internal queues that a packet may pass through a Redhat 9
Linux that acts as a router. Is there also a network card queue
("ifconfig eth0 txqueuelen 1000"? but what is the receiving side "ifconfig
eth0 rxqueuelen 1000" -- tried, but incorrect).

Thanks!
-- Haifeng

Haifeng Zhu wrote:

>
> Hi, folks,
>
> Do you know how to increase the FIFO (both input and output) packet queue
> limits (Default is 100 packets) to, say, 1000 packets ?
>
> I mean, where is the file that defines this default limit ?
>
> Also, this seems to be the protocol independent queue. I want to increase
> all possible internal queues that a packet may pass through a Redhat 9
> Linux that acts as a router. Is there also a network card queue
> ("ifconfig eth0 txqueuelen 1000"? but what is the receiving side "ifconfig
> eth0 rxqueuelen 1000" -- tried, but incorrect).
>
> Thanks!
> -- Haifeng
Hello Haifeng,

this parameter can not be modified, because there is not limit to this
queue.
Each processor has a softnet_data structure, which holds a list with packets
received by the NIC. In this structure, the average lenght of the backlog
queue is stored. Using this number, the congestion level is calculated.
If the congestion level is too high, the kernel will try to solve the
problem, for example by turning the device in the polling mode. A device
won't raise interrupts any more in this mode, so if the processor don't
poll fast enough, packets will be lost.

With kind regards, Alex