Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT

[Nick Piggin]

On Tue, Jan 20, 2009 at 09:56:53PM +0100, Ingo Molnar wrote:
> 
> * Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> >> |       50234816 |     51303520  cache references            +2.12%
> >> |        5428258 |      5583728  cache misses                +2.86%
> >>   
> >
> > Is this I or D, or combined?
> 
> That's last-level-cache references+misses (L2 cache):
> 
>  Bit Position Event Name                UMask Event Select
>  CPUID.AH.EBX
>  3            LLC Reference             4FH   2EH
>  4            LLC Misses                41H   2EH

Oh, _llc_ references/misses? Ouch.

You have, what 32K L1I, 32K L1D, and 4MB L2? And even this microbenchmark
is seeing increased L2 misses by nearly 3%. Hmm, I wonder where that is
coming from? Instruction fetches?

It would be interesting to see how "the oltp" benchmark fares with
CONFIG_PARAVIRT turned on. That workload lives and dies by the cache :)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/