Re: [External] Re: [PATCH] mm: memcontrol: localize mem_cgroup_sockets_enabled() check

[Muchun Song]

On Mon, Oct 12, 2020 at 9:59 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
>
> On Sat, Oct 10, 2020 at 06:45:21PM +0800, Muchun Song wrote:
> > Move the mem_cgroup_sockets_enabled() checks into memcg socket charge
> > or uncharge functions, so the users don't have to explicitly check that
> > condition.
> >
> > This is purely code cleanup patch without any functional change. But
> > move the sk_memcg member of the sock structure to the CONFIG_MEMCG
> > scope.
> >
> > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > ---
> >  include/linux/memcontrol.h      | 78 ++++++++++++++++++++++++++-------
> >  include/net/sock.h              |  5 ++-
> >  include/net/tcp.h               |  3 +-
> >  mm/memcontrol.c                 | 43 +++++++++++++-----
> >  net/core/sock.c                 | 15 +++----
> >  net/ipv4/inet_connection_sock.c |  6 +--
> >  net/ipv4/tcp_output.c           |  3 +-
> >  7 files changed, 111 insertions(+), 42 deletions(-)
>
> Hm, this is almost 3 times as much code.
>
> The sk_memcg saving on !CONFIG_MEMCG is somewhat nice, but it's not
> clear how many users would benefit here. And it adds ifdefs in code.

The 'ifdefs in code' means the initialization of sk_memcg in the sk_clone_lock?
If yes, we can add a new inline initialization function to avoid this.

>
> Also memcg code now has to know about struct sock.

Without this patch, the memcg code also has to know about struct sock.
You can see the code of  mem_cgroup_sk_alloc and mem_cgroup_sk_free.

Thanks.

>
> I'm not quite sure that this is an overall improvement.



-- 
Yours,
Muchun