email@example.com (Måns Rullgård) writes:
> > > > Btw, I just noticed that hard disk throughput is much lower with 2.5
> > > > than 2.4. With 2.4.21-pre5 I get ~40 MB/s, but with 2.5.67 the speed
> > > > drops to 25-30 MB/s. Everything according to hdparm. Is it possible
> > > > that DMA is generally slow for some reason?
> > >
> > > Possible reason is that in 2.4 we've forced reasonable latency timer
> > > value for all PCI devices, while in 2.5 we haven't as yet.
> > Do you mean whatever causes this message (for a 3com NIC)?
> > PCI: Setting latency timer of device 00:05.0 to 64
> > Would that also explain why my hard disks are slow under 2.5? There
> > is no corresponding message for the ide controller (htp374).
> I just checked the troublesome board. Here's what lspci has to say:
> 00:06.0 Display controller: 3DLabs GLINT R3 (rev 01)
> Subsystem: 3DLabs: Unknown device 0121
> Flags: bus master, 66Mhz, medium devsel, latency 0, IRQ 27
> Memory at 0000000009020000 (32-bit, non-prefetchable) [size=128K]
> Memory at 000000000c000000 (32-bit, prefetchable) [size=64M]
> Memory at 0000000010000000 (32-bit, prefetchable) [size=64M]
> Expansion ROM at 0000000009060000 [disabled] [size=64K]
> Capabilities: <available only to root>
> The latency 0 doesn't look too good. What should I do to change it?
I set the latency to 128 using setpci and now I get 66 MB/s. Other
values give slower transfer rates. Is there some other setting that
could improve it even more?
-- Måns Rullgård firstname.lastname@example.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to email@example.com More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:17 EST