Messages in this thread | | | Subject | Re: DMA transfers in 2.5.67 | From | (Måns Rullgård) | Date | 16 Apr 2003 11:30:43 +0200 |
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mru@users.sourceforge.net (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 mru@users.sf.net - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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