Re: IDE performance drop between 2.4.23 and 2.6.0

[Jean-Luc Fontaine <jfontain@free.fr>]

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Linus Torvalds wrote:
|
| On Sat, 27 Dec 2003, Jean-Luc Fontaine wrote:
|
|>I solved the problem in a very strange way. Note that the (b) disk
|>performance only improves after readahead has been increased on another
|>(c) drive! (the (c) drive performance was also increased by to 2.4
|>levels but is not shown here). I could reliably repeat this behavior
|>after rebooting.
|>
|>Can any IDE expert explain it?
|
|
| Looks like a bug. If you don't access hdc,

hdc is / for 2.6, whereas hdb is used for 2.4. So hdc was obviously
accessed prior to this test.

| then the read-ahead on hdc
| shouldn't matter. I wonder if the read-ahead code (either the setting or
| the reading) gets the value from the wrong queue or something.

Or could this set something in the VIA chipset? I'll take a look in
/proc/ide/via and report if needed.

Let me know if you need more tests to be run.

- --
Jean-Luc Fontaine  mailto:jfontain@free.fr  http://jfontain.free.fr/
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