Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5

[jamal <hadi@cyberus.ca>]

Some data on lesser worthy cards (i.e 10/100) on 2.4.7
can be found at:
http://www.cyberus.ca/~hadi/247-res/

cheers,
jamal

On Tue, 2 Oct 2001, Robert Olsson wrote:

>
>
> Hello!
>
> Jamal mentioned some about the polling efforts for Linux. I can give some
> experimental data here with GIGE. Motivation, implantation etc is in paper
> to presented at USENIX Oakland.
>
> Below a IP forwarding test. Injected 10 Million 64 byte packets into eth0 at
> a speed of 890.000 p/s received and routed and TX:ed on eth1.
>
> PIII @ 933 MHz. Kernel UP 2.4.10 with polling patch the are NIC's e1000
> eth0 (irq=24) and eth1 (irq=26)
>
>
> Iface   MTU Met  RX-OK RX-ERR RX-DRP RX-OVR  TX-OK TX-ERR TX-DRP TX-OVR Flags
> eth0   1500   0 4031309 7803725 7803725 5968699     22      0      0      0 BRU
> eth1   1500   0     18      0      0      0 4031305      0      0      0 BRU
>
>
> The RX-ERR, RX-DRP are bugs from the e1000 driver. Anyway we getting 40% of
> packet storm routed. With a estimated throughput is about 350.000 p/s
>
>  irq       CPU0
>  24:      80652   IO-APIC-level  e1000
>  26:         41   IO-APIC-level  e1000
>
> The for RX (polling) we use only 24 interrupts. TX is mitigated (not polled)
> in this run. We see a lot more interrupts for same amount of packets. I think
> we can actually tune this a bit... And I should also say that RxIntDelay=0
> (e1000 driver). So there is no latency before the driver register for polling
> by kernel.
>
> USER       PID %CPU %MEM  SIZE   RSS TTY STAT START   TIME COMMAND
> root         3  3.0  0.0     0     0  ?  SWN  12:51   0:11 (ksoftirqd_CPU0)
>
> The polling (softirq) now handled by ksoftirqd  but I have seen a path from
> Ingo that schedules without the need for ksoftirqd.
>
> Also note that during poll we disable only RX interrupts so all other device
> interrupts/functions are handled properly.
>
> And tulip variants of this is in production use and seems very solid. The
> kernel code part holds ANK-trademark. :-)
>
> Cheers.
>
> 						--ro
>