On Thu, Mar 13, 2025 at 12:01:14PM -0400, Johannes Weiner wrote:
> > void split_page_memcg(struct page *first, unsigned order)
> > {
> > - struct folio *folio = page_folio(first);
> > + struct obj_cgroup *objcg = page_objcg(first);
> > unsigned int i, nr = 1 << order;
> >
> > - if (mem_cgroup_disabled() || !folio_memcg_charged(folio))
> > + if (!objcg)
> > return;
>
> mem_cgroup_disabled() is a jump label, so a bit cheaper than the
> branch. Can you keep that and do page_objcg() after it?
I think this might be better?
-static struct obj_cgroup *page_objcg(const struct page *first)
+static struct obj_cgroup *page_objcg(const struct page *page)
{
- unsigned long memcg_data = first->memcg_data;
+ unsigned long memcg_data = page->memcg_data;
- if (!memcg_data)
+ if (mem_cgroup_disabled() || !memcg_data)
return NULL;
I'd expect the compiler to inline page_objcg() into its caller and
optimise away the NULL test if mem_cgroup_disabled().
