Re: [PATCH] mm/list_lru: dont make them memcg aware if kmem is disabled

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 27 Nov 2020 20:21:11 +1100 Balbir Singh <bsingharora@gmail.com> wrote:

> On Thu, Nov 26, 2020 at 01:10:18PM +0100, Vlastimil Babka wrote:
> > On 11/26/20 5:30 AM, Balbir Singh wrote:
> > > When alloc_super() allocates list_lrus for dentries and inodes
> > > they are made memcg aware if KMEM is compiled in, we should
> > > also check if kmem was disabled at runtime.
> > > 
> > > This overhead is about 32 bytes extra per possible nodes per caller
> > > of list_lru_init()
> > > 
> > > Signed-off-by: Balbir Singh <bsingharora@gmail.com>
> > 
> > I'd rather export cgroup_memory_nokmem and make cgroup_kmem_disabled()
> > inline, put it next to memcg_kmem_enabled() and explain in comments what
> > each means.
> > 
> > And ideally, the current memcg_kmem_enabled() should be named e.g.
> > memcg_kmem_active(), and then the new cgroup_kmem_disabled() could be named
> > memcg_kmem_enabled(). But that's churn and potential future backport hazard,
> > so dunno.
> 
> Yes, I am happy with whatever approach works to fast track the patches
> 
> Andrew, thoughts/comments?
> 

Your original changelog doesn't make the case that the patch should be
fast tracked, so it looks like there's missing information.  Please
don't miss information ;)

If we're looking for a backportable quickfix for the
not-yet-really-explained problem then yes, Vlastimil's suggestion (as a
high-priority patch and a separate low-priority patch) sounds good.

It is rather a twisty maze of identifiers, so please do comment
everything well.