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Re: Darwin disk I/O - better interactive response

At 8:38 PM -0800 1/23/01, Peter Bierman wrote:
> >> Even if I held that position, it would be wrong of me to assume that
>>> everyone else uses computers the same way I do.
>>
>>Good. Then you might agree that some of us don't want to use Darwin as
>>merely a server or merely a BSD variant, but would like to see it DEVELOP
> >into a more Mac like PERSONAL computer OS...
>
>You guys are drifting waaaaay off into meta-arguments.

I don't think so. The details of how to attain User Experience goals are at least as important as other aspects.

>If you have a specific change that you think should be made to darwin, we can discuss that.
>
>We talked about ordering the write queue, and it was mentioned that this would be counterproductive, since the device firmware now does this for us.

It doesn't have to. There is no requirement that the disk driver dump a whole bunch of requests on the drive. It can be smart and dole them out to the drive, retaining its prerogative to order the queue as directed from above. (With one caveat: Kirk McKusick just reminded me that two contiguous I/O requests across tracks probably have to both be queued up in the device if you want to avoid missing a revolution between them.)

>We can talk about fine tuning the scheduler, but this is something that people spend months on, using as much real world data as possible, and it's still a black art, capable of causing all sorts of priority inversion problems. It's a subject best left lightly discussed unless you have a *specific* change that you want to make, and then you'd better be prepared to defend your changes.

Not all ideas must be implemented by their proposers to be worth doing. Your CEO comes to mind...

>You have the code. If one has a point to prove, then one should prove it.

If one is being paid to hack on Darwin, yes. Unfortunately I am not, and all I can afford to do is lobby.

>As for Apple's goals for darwin... they're simple. We want it to be fast. :-)

Goals, like other things, should be as simple as possible but no simpler. That's too simple.

Dave

References: 
 >Re: Darwin disk I/O - better interactive response (From: Peter Bierman <email@hidden>)



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