在 2022/8/13 上午8:44，“Yosry Ahmed”<yosryahmed@xxxxxxxxxx> 写入:
> On Fri, Aug 12, 2022 at 2:56 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote:
> >
> > +Andrew & linux-mm
> >
> > On Thu, Aug 11, 2022 at 5:12 PM Roman Gushchin <roman.gushchin@xxxxxxxxx> wrote:
> > >
> > > On Thu, Aug 11, 2022 at 04:19:13PM +0800, liliguang wrote:
> > > > From: Li Liguang <liliguang@xxxxxxxxx>
> > > >
> > > > Kswapd will reclaim memory when memory pressure is high, the
> > > > annonymous memory will be compressed and stored in the zpool
> > > > if zswap is enabled. The memcg_kmem_bypass() in
> > > > get_obj_cgroup_from_page() will bypass the kernel thread and
> > > > cause the compressed memory not charged to its memory cgroup.
> > > >
> > > > Remove the memcg_kmem_bypass() and properly charge compressed
> > > > memory to its corresponding memory cgroup.
> > > >
> > > > Signed-off-by: Li Liguang <liliguang@xxxxxxxxx>
> > > > ---
> > > > mm/memcontrol.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > > index b69979c9ced5..6a95ea7c5ee7 100644
> > > > --- a/mm/memcontrol.c
> > > > +++ b/mm/memcontrol.c
> > > > @@ -2971,7 +2971,7 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
> > > > {
> > > > struct obj_cgroup *objcg;
> > > >
> > > > - if (!memcg_kmem_enabled() || memcg_kmem_bypass())
> > > > + if (!memcg_kmem_enabled())
>
>
> Won't the memcg_kmem_enabled() check also cause a problem in that same
> scenario (e.g. if CONFIG_MEMCG_KMEM=n)? or am I missing something
> here?
>
Please notes that the return value is a pointer to obj_cgroup, not memcg.
If CONFIG_MEMCG_KMEM=n or memcg kmem charge is disabled, the NULL need
to be returned.
> >
> > > > return NULL;
> > > >
> > > > if (PageMemcgKmem(page)) {
> > > > --
> > > > 2.32.0 (Apple Git-132)
> > > >
> > >
> > > Hi Li!
> > >
> > > The fix looks good to me! As we get objcg pointer from a page and not from
> > > the current task, memcg_kmem_bypass() doesn't makes much sense.
> > >
> > > Acked-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
> > >
> > > Probably, we need to add
> > > Fixes: f4840ccfca25 ("zswap: memcg accounting")
> > >
> > > Thank you!
> >
> > You can add:
> >
> > Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> >
