Messages in this thread | | | Date | Thu, 24 Sep 2020 13:29:11 -0700 | From | Roman Gushchin <> | Subject | Re: [PATCH v1 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data |
| |
On Thu, Sep 24, 2020 at 03:53:56PM -0400, Johannes Weiner wrote: > On Tue, Sep 22, 2020 at 01:36:58PM -0700, Roman Gushchin wrote: > > To gather all direct accesses to struct page's memcg_data field > > in one place, let's introduce 4 new helper functions to use in > > the slab accounting code: > > struct obj_cgroup **page_obj_cgroups(struct page *page); > > struct obj_cgroup **page_obj_cgroups_check(struct page *page); > > bool set_page_obj_cgroups(struct page *page, struct obj_cgroup **objcgs); > > void clear_page_obj_cgroups(struct page *page); > > > > They are similar to the corresponding API for generic pages, except > > that the setter can return false, indicating that the value has been > > already set from a different thread. > > > > Signed-off-by: Roman Gushchin <guro@fb.com> > > Reviewed-by: Shakeel Butt <shakeelb@google.com> > > --- > > include/linux/memcontrol.h | 80 ++++++++++++++++++++++++++++++++++++++ > > mm/memcontrol.c | 4 +- > > mm/slab.h | 27 ++----------- > > 3 files changed, 85 insertions(+), 26 deletions(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 3313e7c21534..ab3ea3e90583 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -409,6 +409,86 @@ static inline void clear_page_mem_cgroup(struct page *page) > > page->memcg_data = 0; > > } > > > > +#ifdef CONFIG_MEMCG_KMEM > > +/* > > + * page_obj_cgroups - get the object cgroups vector associated with a page > > + * @page: a pointer to the page struct > > + * > > + * Returns a pointer to the object cgroups vector associated with the page, > > + * or NULL. This function assumes that the page is known to have an > > + * associated object cgroups vector. It's not safe to call this function > > + * against pages, which might have an associated memory cgroup: e.g. > > + * kernel stack pages. > > + */ > > +static inline struct obj_cgroup **page_obj_cgroups(struct page *page) > > +{ > > + return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); > > page_mem_cgroup() has a VM_BUG_ON() if the page is in fact a slab > type. Should this also check that if memcg_data is set, it MUST have > the lower bit set?
Absolutely, patch 3 does this after the formalization of the bit as a flag.
> > In line with page_memcg(), I think page_objcgs() would be nicer.
Ok to me.
Thanks!
| |