Messages in this thread | | | From | Nick Piggin <> | Subject | Re: Update cacheline size on X86_GENERIC | Date | Sat, 11 Oct 2008 19:29:19 +1100 |
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On Saturday 11 October 2008 19:08, Andi Kleen wrote: > > I guess there is a reasonable argument to not care about P4 so > > I don't think it is. Ignoring old systems would be a mistake > and the wrong signal. One of Linux's forte over the competition > was always to run reasonable on older systems too.
I think there is a reasonable argument: and that is that most multiprocessor P4 systems in production and using a GENERIC (ie. probably not custom but probably vendor compiled) kernel is not likely to be upgraded to a 2.6.28+ based GENERIC kernel.
I also think there are reasonable arguments the other way, and I personally also think it might be better to leave it 128 (even if it is unlikely, introducing a regression is not good).
> There are millions and millions of P4s around. > And they're not that old, they're still shipping in fact.
Still shipping in anything aside from 1s systems?
> And the point of GENERIC was to be a reasonable default on all > systems. > > If you want to optimize for a specific CPU you're always free > to compile the kernel for that. But GENERIC should be really > GENERIC. > > > much in today's GENERIC kernel. If it is worth around 1% on tpc > > on a more modern architecture, that is a pretty big motivation > > to change it too... > > TPC is a extreme case, it is extremly cache bound.
Still, 1% there is a large increase.
> Besides I suspect the TPC issue could be fixed with a minimal > tweaks without breaking other systems.
That would be nice. It would be interesting to know what is causing the slowdown.
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