Re: [PATCH v1 2/4] mm: memcg: merge multiple page_counters into a single structure

Roman Gushchin
2024-05-03T21:18:37Z

On Fri, May 03, 2024 at 02:11:17PM -0700, Shakeel Butt wrote:
> On Fri, May 03, 2024 at 01:18:33PM -0700, Roman Gushchin wrote:
> [...]
> > enum mem_counter_type {
> > +#ifdef CONFIG_MEMCG
> > MCT_MEMORY, /* cgroup v1 and v2 */
> > MCT_SWAP, /* cgroup v2 only */
> > MCT_MEMSW = MCT_SWAP, /* cgroup v1 only */
> > MCT_KMEM, /* cgroup v1 only */
> > MCT_TCPMEM, /* cgroup v1 only */
> > +#endif
> > +#ifdef CONFIG_CGROUP_HUGETLB
> > + MCT_HUGETLB_MAX = __MCT_HUGETLB_MAX,
> > +#endif
> > + __MCT_NR_ITEMS,
> > };
> >
>
> Thanks for the awesome work. I haven't gone through all the patches yet
> but wanted to ask a quick question. In the above enum are you trying to
> do a union between memcg and hugetlb? It gave me a big pause to
> understand what you are trying to do.

Yep, sort of. So the page_counter structure supports N independent
counters, where N is sufficient enough for both memcg and hugetlb cases.

MCT_MEMORY, MCT_SWAP etc are used directly in the memcontrol.c code,
while hugetlb code just indexes. MCT_HUGETLB_MAX magic is needed to define
N at the compile time.

Thanks!