[Python-Dev] Opcode cache in ceval loop

[Sven R. Kunze]

On 04.02.2016 16:57, Matthias Bussonnier wrote:
>> On Feb 3, 2016, at 13:22, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
>>
>>
>> An ideal way would be to calculate a hit/miss ratio over time
>> for each cached opcode, but that would be an expensive
>> calculation.
> Do you mean like a sliding windows ?
> Otherwise if you just want a let's say 20% miss threshold, you increment by 1 on hit,
> and decrement by 4 on miss.

Division is expensive.

>
> On Feb 3, 2016, at 13:37, Sven R. Kunze <srkunze at mail.de> wrote:
>
>> On 03.02.2016 22:22, Yury Selivanov wrote:
>>> One way of tackling this is to give each optimized opcode
>>> a counter for hit/misses.  When we have a "hit" we increment
>>> that counter, when it's a miss, we decrement it.
>> Within a given range, I suppose. Like:
>>
>> c = min(c+1, 100)
>
> Min might be overkill, maybe you can use a or mask, to limit the windows range
> to 256 consecutive call ?

Sure, that is how I would have written it in Python. But I would suggest 
an AND mask. ;-)

Best,
Sven