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SubjectRe: Default cache_hot_time value back to 10ms
Nick Piggin <> wrote:
> Andrew Morton wrote:
> > "Chen, Kenneth W" <> wrote:
> >
> >>This value was default to 10ms before domain scheduler, why does domain
> >> scheduler need to change it to 2.5ms? And on what bases does that decision
> >> take place? We are proposing change that number back to 10ms.
> >
> >
> > It sounds like this needs to be runtime tunable?
> >
> I'd say it is probably too low level to be a useful tunable (although
> for testing I guess so... but then you could have *lots* of parameters
> tunable).

This tunable caused an 11% performance difference in (I assume) TPCx.
That's a big deal, and people will want to diddle it.

If one number works optimally for all machines and workloads then fine.

But yes, avoiding a tunable would be nice, but we need a tunable to work
out whether we can avoid making it tunable ;)

Not that I'm soliciting patches or anything. I'll duck this one for now.
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