[Question] mm/vmpressure.c: ilog2 calculation in constant

[Question] mm/vmpressure.c: ilog2 calculation in constant

[torvic9]

Hello,

in mm/vmpressure.c, we have defined this constant:

  static const unsigned int vmpressure_level_critical_prio = ilog2(100 / 10);

My question is: Why do we calculate ilog2 instead of simply setting the constant to '3'?
Then, I guess, we could also get rid of the log2.h include.
Note that this is just a question, not a request, as I'm sure there is a reason for this.
(given the help text in the comment just above)

Greetings,
Tor Vic

Re: [Question] mm/vmpressure.c: ilog2 calculation in constant

[David Hildenbrand]

On 28.05.21 14:08, torvic9@mailbox.org wrote:
> Hello,
> 
> in mm/vmpressure.c, we have defined this constant:
> 
>    static const unsigned int vmpressure_level_critical_prio = ilog2(100 / 10);
> 
> My question is: Why do we calculate ilog2 instead of simply setting the constant to '3'?

My best guess is that it's in place to a) increase readability b) make 
it easier to adjust. The compiler will optimize it out either way, so we 
don't really care.

Having that said: it doesn't increase readability on my end. But I only 
took a quick glimpse. Maybe the "100 / 10 == 10" here is the magic bit 
also mentioned in the comment "when scanning depth is ~10%". So it can 
be adjusted "more easily" eventually ... at least not by me.

-- 
Thanks,

David / dhildenb