[LARTC] Performance problem on a linux bridge used for shaping.

[Alexandru Dragoi <alex@zoomnet.ro>]

Hello,

Here is the situation. There is a machine with 3 intel gigabit card, 2
of them on PCI-X and in bridge, the 3rd is used only for management
access. The machine is a dual Xeon 2.8GHz with HT. With 2.6.8 kernel
from debian (testing) and htb with u32 on, i usually get about 30-40%
software interrupts on CPU0 and CPU2, and without htb and u32, 10% less.
Now, if I boot with 2.6.17.9 kernel, first all irqs are on same CPU. I
managed with smp_afinity to "move" irq of one card to a different CPU.
In these circumstances, I have about 20% or a little less soft
interrupts on each CPU without shaping, but about 60-70% os soft
interrupts with shapping, and sometimes there is packet loss, also
dropped packets are shown on ifconfig. The htb script is same. I have
u32 performance counters enabled on u32 in 2.6.17.9. I also have NAPI,
of course. I can't think on anything else that can cause the problem,
but seem to be something in the kernel. Here is the output of lspci:

# lspci
0000:00:00.0 Host bridge: Intel Corporation E7320 Memory Controller Hub
(rev 0a)
0000:00:00.1 ff00: Intel Corporation E7320 Error Reporting Registers
(rev 0a)
0000:00:02.0 PCI bridge: Intel Corporation E7525/E7520/E7320 PCI Express
Port A (rev 0a)
0000:00:03.0 PCI bridge: Intel Corporation E7525/E7520/E7320 PCI Express
Port A1 (rev 0a)
0000:00:1c.0 PCI bridge: Intel Corporation 6300ESB 64-bit PCI-X Bridge
(rev 02)
0000:00:1d.0 USB Controller: Intel Corporation 6300ESB USB Universal
Host Controller (rev 02)
0000:00:1d.1 USB Controller: Intel Corporation 6300ESB USB Universal
Host Controller (rev 02)
0000:00:1d.4 System peripheral: Intel Corporation 6300ESB Watchdog Timer
(rev 02)
0000:00:1d.5 PIC: Intel Corporation 6300ESB I/O Advanced Programmable
Interrupt Controller (rev 02)
0000:00:1d.7 USB Controller: Intel Corporation 6300ESB USB2 Enhanced
Host Controller (rev 02)
0000:00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 0a)
0000:00:1f.0 ISA bridge: Intel Corporation 6300ESB LPC Interface
Controller (rev 02)
0000:00:1f.2 IDE interface: Intel Corporation 6300ESB SATA Storage
Controller (rev 02)
0000:00:1f.3 SMBus: Intel Corporation 6300ESB SMBus Controller (rev 02)
0000:03:02.0 Ethernet controller: Intel Corporation 82544EI Gigabit
Ethernet Controller (Copper) (rev 02)
0000:03:03.0 Ethernet controller: Intel Corporation 82544EI Gigabit
Ethernet Controller (Copper) (rev 02)
0000:04:02.0 VGA compatible controller: ATI Technologies Inc Rage XL
(rev 27)
0000:04:03.0 Ethernet controller: Intel Corporation 82541GI Gigabit
Ethernet Controller (rev 05)

The traffic is somewhere at 40kpps of traffic and 120mbit up,
120mbit/down. Suggestions about better hardware and kernel, or links
with docs about these are really welcomed.

Bye

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