Re: Default cache_hot_time value back to 10ms

[Nick Piggin]

Andrew Morton wrote:

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

True. But 2.5 I think really is too low (for anyone, except maybe a
CPU with no/a tiny L2 cache).

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

Yeah.. 10ms may bring up idle times a bit on other workloads. Judith
had some database tests that were very sensitive to this - if 10ms is
OK there, then I'd say it would be OK for most things.

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

Heh. I think it would be good to have a automatic thingy to tune it.
A smarter cache_decay_ticks calculation would suit.

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

OK. Any idea when 2.6.9 will be coming out? :)
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