RE: [RFC 00/11] Remove 'order' argument from many mm functions

Weiny, Ira
2019-05-09T16:48:45Z

> On Wed, May 08, 2019 at 06:58:09PM -0700, Ira Weiny wrote:
> > On Mon, May 06, 2019 at 09:05:58PM -0700, Matthew Wilcox wrote:
> > > It's possible to save a few hundred bytes from the kernel text by
> > > moving the 'order' argument into the GFP flags. I had the idea
> > > while I was playing with THP pagecache (notably, I didn't want to add an
> 'order'
> > > parameter to pagecache_get_page())
> ...
> > > Anyway, this is just a quick POC due to me being on an aeroplane for
> > > most of today. Maybe we don't want to spend five GFP bits on this.
> > > Some bits of this could be pulled out and applied even if we don't
> > > want to go for the main objective. eg rmqueue_pcplist() doesn't use
> > > its gfp_flags argument.
> >
> > Over all I may just be a simpleton WRT this but I'm not sure that the
> > added complexity justifies the gain.
>
> I'm disappointed that you see it as added complexity. I see it as reducing
> complexity. With this patch, we can simply pass GFP_PMD as a flag to
> pagecache_get_page(); without it, we have to add a fifth parameter to
> pagecache_get_page() and change all the callers to pass '0'.

I don't disagree for pagecache_get_page().

I'm not saying we should not do this. But this seems odd to me.

Again I'm probably just being a simpleton...
Ira