Re: [Qemu-devel] [PATCH v3 11/11] translate-all: add tb hash bucket info to 'info jit' dump

[Richard Henderson]

On 04/26/2016 07:43 PM, Emilio G. Cota wrote:
> How does the following look?
> 
> Example with good hashing, i.e. func5(phys_pc, pc, flags):
> TB count            704242/1342156
> [...]
> TB hash buckets     386484/524288 (73.72% used)
> TB hash occupancy   32.57% avg chain occupancy. Histogram: 
> 0-10%▆▁█▁▁▅▁▃▁▁90-100%
> TB hash avg chain   1.02 buckets. Histogram: 1█▁▁3
> 
> Example with bad hashing, i.e. func5(phys_pc, 0, 0):
> TB count            710748/1342156
> [...]
> TB hash buckets     113569/524288 (21.66% used)
> TB hash occupancy   10.24% avg chain occupancy. Histogram: 
> 0-10%█▁▁▁▁▁▁▁▁▁90-100%
> TB hash avg chain   2.11 buckets. Histogram: 1▇▁▁▁▁▁▁▁▁▁93
> 
> Note that:
> 
> - "TB hash avg chain" does _not_ count empty buckets. This gives
>   an idea of how many buckets a typical hit goes through.
> 
> - "TB hash occupancy" _does_ count empty buckets. It is called
>   "avg chain occupancy" and not "avg occupancy" because the
>   counts are only valid per-chain due to the seqlock protecting
>   each chain.

Looks really good.


r~