Re: [PATCHv2 3/6] zsmalloc: fine-grained inuse ratio based fullness grouping

[Minchan Kim]

On Wed, Mar 01, 2023 at 05:55:44PM +0900, Sergey Senozhatsky wrote:
> On (23/02/28 14:53), Minchan Kim wrote:
> > BTW, I still prefer the enum instead of 10 define.
> > 
> > enum fullness_group {
> >     ZS_EMPTY,
> >     ZS_INUSE_RATIO_MIN,
> >     ZS_INUSE_RATIO_ALMOST_FULL = 7,
> >     ZS_INUSE_RATIO_MAX = 10,
> >     ZS_FULL,
> >     NR_ZS_FULLNESS,
> > }
> 
> For educational purposes, may I ask what do enums give us? We
> always use integers - int:4 in zspage fullness, int for arrays
> offsets and we cast to plain integers in get/set stats. So those
> enums exist only at declaration point, and plain int otherwise.
> What are the benefits over #defines?

Well, I just didn't like the 12 hard coded define *list* values
and never used other places except zs_stats_size_show since
I thought we could handle zs_stats_size_show in the loop without
the specific each ratio definary.

Furthermore, above example, the special ZS_INUSE_RATIO_MAX will
be definary instead of hard coded 10.

    ZS_INUSE_RATIO_MAX = ZS_INUSE_RATIO_MIN + ZS_INUSER_RATIO_CLASS_SIZE

so, if we want to change the ratio later, we would need minimal
changes all the places instead of changing all the hard codeded
definary.