Re: VIA IDE performance under 2.6.0-test7/8?

[Knut Petersen]

Hi James!

> Can you also send the output from "cat /proc/interrupts".
> It looks like you are not using IO-APIC, but instead using XT-PIC.
> XT-PIC is a lot slower than IO-APIC.

Reading the  previous messages I compared the SuSE 2.4.20-4GB and the 
2.6.0-test8-bk1 kernel.

The mainboard is a VIA EPIA 5000 (cpu Via Eden 533 Mhz, Via 8601A 
Northbridge, VT8231 Southbridge)

hdparm -I /dev/hd? displays no difference ... udma2 is the used mode.

hdparm -T /dev/hd? measures transfer rates of 60-63 MB/s, there is no 
significant difference between
the kernel versions.

hdparm -t /dev/hd? mesasures 18 MB/s for kernel 2.6.0-test8-bk1 and 27 
MB/s for kernel 2.4.20.
This is a significant  :-(

2.4.20 gives almost exactly 50% better performance compared to 
2.6.0-test8 ... is this pure accident or could this give a hint?

> Just turn on SMB support in the "make menuconf", and it should enable 
> IO-APIC.

Compiling the kernel with and without smb support as well as trying the 
other APIC related new configuration options
does change nothing.  There is allways a "No local APIC present or 
hardware disabled" message. I believe that there
really is no IO-APIC, at least I found no related BIOS configuration option.

/proc/interrupts indicates an XT-PIC for both kernel versions.

IRQ setup is identical, IDE IRQs are not shared with any other devices.

The drive is the only drive attached.

Playing around with different read-ahead values does not help.

Any ideas?

cu,
Knut Petersen


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