Re: [PATCH] [RFC][GSoC][PATCH] attr: use local repository state in read_attr

> Tian Yuchen<a3205153416@gmail.com> writes:
> 
>> Junio C Hamano<gitster@pobox.com> writes:
>>
>>   >The codepath read_attr() is in is usually not that hot but it is not
>>   >cheap.
>>
>> I'm a bit curious—under what circumstances would calling this method
>> result in significant performance regression?
> Significant?  I dunno.
> 
> And quite honestly, I do not care about significance very much in a
> case like this.  Doing things that do not make sense, like checking
> the same configuration variable again and again when you_know_ that
> you never switched to a different repository since you last checked,
> is simply wrong.  It burdens the readers with unnecessary cognitive
> load by making them wonder why you do such a nonsensical thing.
> 
> The read_attr() is called during an attr stack construction, which
> traverses the directory hierarchy of a single repositry's working
> tree (we do not traverse across submodule boundaries), and the same
> istate (i.e., index contents) structure is passed around throughout
> the callchain.  The repository instance at istate->repo may be a
> good place to store "am I bare?" bit that is computed just once and
> reused whenever we need to know, like in the funcion under
> discussion.