Re: [PATCHv4 8/9] Documentation: document zram pages_per_pool_page attribute

Sergey Senozhatsky
2022-11-11T10:34:33Z

On (22/11/10 18:20), Minchan Kim wrote:
> > diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst
> > index 010fb05a5999..4cb287520d45 100644
> > --- a/Documentation/admin-guide/blockdev/zram.rst
> > +++ b/Documentation/admin-guide/blockdev/zram.rst
> > @@ -112,7 +112,29 @@ to list all of them using, for instance, /proc/crypto or any other
> > method. This, however, has an advantage of permitting the usage of
> > custom crypto compression modules (implementing S/W or H/W compression).
> >
> > -4) Set Disksize
> > +4) Set pages per-pool page limit: Optional
> > +==========================================
> > +
> > +zsmalloc pages can consist of up to ZS_DEFAULT_PAGES_PER_ZSPAGE (single)
> > +physical pages. The exact number is calculated for each zsmalloc size
> > +class during zsmalloc pool creation. ZRAM provides pages_per_pool_page
> > +device attribute that lets one adjust that limit (maximum possible value
> > +is ZS_MAX_PAGES_PER_ZSPAGE). The default limit is considered to be good
> > +enough, so tweak this value only when the changes in zsmalloc size classes
> > +characteristics are beneficial for your data patterns. The limit on the
> > +pages per zspages (currently) should be in [1,16] range; default value
> > +is 4.
>
> I think we need to introudce pros and cons for user to decide it since
> it's not familiar with admin. I think It would need more explanation about
> zsmalloc internal(especailly zspage and size classes)

OK, agreed. I have quite a bit of info in the 0002 commit messages.
I can copy-paste some of those bits and edit them. We also have
some info the internal doc, which I can also use as a "source of
inspiration".