> Hello. Perhaps someone can comment on my PCI device settings:
Latency timer is 255 for all devices of your system. These value is
obviously too large in theory (modulo chip bugs), but will not have bad
effects on your system, in my opinion, since your devices are not using
large bursts over the PCI.
The NCR 810 is using 16 DWORDS max bursts, the ethernet controller is
probably not able to sustain larger burst and the display controller will
probably never act as a master. So any value greater than 30 for the
latency timer of PCI devices will not make significant differences even on
heavy system load, in my opinion. And on heavy load, your system will
probably not need more than 30% of the PCI BUS bandwidth. That's the case
for most of existing systems that are so able to accomodate very different
latency timer values without any stomach problems.
This would be a different situation if your system was using very fast
devices capable of large bursting accross the PCI BUS. For example,
Ultra2/Wide SCSI driving several fast hard disks + video input + a couple
of 100 Mbit/sec eth boards at the same time.
My initial complaint was against net drivers silently setting the latency
timer to its largest possible value and my goal was certainly not to
launch some latency timer paranoia.
Regards,
Gerard.
> PCI devices found:
> Bus 0, device 13, function 0:
> Display controller: DEC DC21030 (TGA) (rev 3).
> Medium devsel. Fast back-to-back capable. Master Capable.
> Latency=255.
> Prefetchable 32 bit memory at 0x8000000.
> Bus 0, device 11, function 0:
> Ethernet controller: DEC DC21040 (rev 36).
> Medium devsel. Fast back-to-back capable. IRQ 15. Master Capable.
> Latency=255.
> I/O at 0x8000.
> Non-prefetchable 32 bit memory at 0x11000000.
> Bus 0, device 7, function 0:
> Non-VGA device: Intel 82378IB (rev 132).
> Medium devsel. Master Capable. No bursts.
> Bus 0, device 6, function 0:
> SCSI storage controller: NCR 53c810 (rev 2).
> Medium devsel. IRQ 11. Master Capable. Latency=255.
> I/O at 0x8800.
> Non-prefetchable 32 bit memory at 0x11001000.
>
> Notice the CFLT of every single PCI device in my system is 255. Perhaps
> someone can explain? The system is AlphaStation 200 (Avanti, 21064A)
> booting from SRM console. The kernel is 2.0.35.
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