Messages in this thread | | | Date | Thu, 3 Dec 1998 17:04:40 +0100 (MET) | From | (Alex A.M.R. Slingerland) | Subject | [OFFTOPIC] Re: IDE-DMA strangeness (another one) |
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[snip Rik's account of HD performance]
Andre M. Hedrick wrote: >I get 12-13 rates with UDMA chipset amd UDMA Drive.......... >My oldest UDMA drive is a brick at 8.7 a Quantum FB 3.2 ST >Next oldest UDMA drive is better at 9.8, a Quantum FB 6.4 ST >Here is the drive is better at 10.92, a Quantum FB 8.4 SE >The newest pair of drives are at 12.38, are Maxtor 6.8 > >As you see it is the drive.........all of these numbers are on the same >chipset.........the Quantum FB ST's are from memory.
Hmm. Assuming those are hdparm numbers and not e.g. bonnie:
On my ASUS P5A with Ali 5 chipset, a Quantum EL 5.1 (and K6-2-300, 128Mb PC100 SDRAM), with hdparm 3.5 on Linux 2.1.126 and later, I get something like:
$ hdparm -tT /dev/hda bla-bla 128Mb: 51 Mb/s bla-bla 64Mb : 11.19 Mb/s
It's using PIO 4 (as linux doesn't currently support UDMA/DMA on my Ali chipset) and multcount is set to 8, io to 32 bits.
Is this drive actually doing 11 Mb/s in PIO (not that I mind)?
Does this mean I'm using (roughly, at least, on average) 11.19/16.66 ~= 2/3 of the CPU's processing power PIO-ing things off the drive (in e.g. a long running "just read and do nothing with the read data" test)? If true, the above suggests that neither the CPU nor the 16.66 Mb/s interface is a bottleneck (in the hdparm test), as this leaves about 1/3 of the CPU power for linux' housekeeping/context-switching/whatnot and hdparm, which I'm guessing would do. Or could I still expect a (significant) increase in _hdparm_measured_throughput_ when using UDMA/DMA (i.e., ignoring the effect the lower CPU load would/might have on a real app)?
Regs, Alex.
PS. Andre: Please consider the pain and suffering you are causing by mentioning that ide-update-13 is expected "soon", and it still not appearing on your site days later ;) --
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