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SubjectRe: [PATCH] O11int for interactivity

William Lee Irwin III wrote:

>On Tue, Aug 05, 2003 at 10:56:16AM +1000, Nick Piggin wrote:
>>I'm an IO scheduler type person! What help do you need? I haven't been
>>following the thread.
>I'm not sure it was in the thread. Basically, the testers appear to
>associate skips with changes in writeout and/or readin behavior (either
>large amounts of writeout or low amounts of readin), though the effect
>of behavior similar to that surrounding a skip doesn't appear to
>guarantee a skip.


snip vmstat

>The load IIRC was some kind of io to an IDE disk while xmms played.
>About all I can tell is that when there is a skip, bi is low, but
>the converse does not hold. This appears to be independent of io
>scheduler (I had them try deadline too), and I'm very unsure what to
>make of it. I originally suspected thundering herds from waitqueue
>hashing but things appear to contradict that given the low cs rates.

So yeah it could easily be that for example the cpu scheduler is
causing the skip and the low IO rates.

>I'm collecting instrumentation patches to see what's going on. The
>first order of business is probably getting the testers to run with
>sleepometer to see if and where they're blocking, but given the io bits
>that are observable some elevator instrumentation might help too (and
>whatever it takes to figure out if a driver is spinning wildly too!).

Let me know if you come up with anything significant ;)

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