Re: [PATCH next-20130703] net: sock: Add ifdef CONFIG_MEMCG_KMEM formem_cgroup_sockets_{init,destroy}
From: Michal Hocko
Date: Wed Jul 03 2013 - 12:34:36 EST
On Wed 03-07-13 18:11:28, Sedat Dilek wrote:
>
On Wed, Jul 3, 2013 at 5:59 PM, Michal Hocko <mhocko@xxxxxxx> wrote:
>
> On Wed 03-07-13 17:53:21, Sedat Dilek wrote:
>
>> On Wed, Jul 3, 2013 at 5:20 PM, Michal Hocko <mhocko@xxxxxxx> wrote:
>
>> > On Wed 03-07-13 20:51:00, Li Zefan wrote:
>
>> > [...]
>
>> >> [PATCH] memcg: fix build error if CONFIG_MEMCG_KMEM=n
>
>> >>
>
>> >> Fix this build error:
>
>> >>
>
>> >> mm/built-in.o: In function `mem_cgroup_css_free':
>
>> >> memcontrol.c:(.text+0x5caa6): undefined reference to
>
>> >> 'mem_cgroup_sockets_destroy'
>
>> >>
>
>> >> Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
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>> >> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
>
>> >> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
>
>> >
>
>> > I am seeing the same thing I just didn't get to reporting it.
>
>> > The other approach is not bad as well but I find this tiny better
>
>> > because mem_cgroup_css_free should care only about a single cleanup
>
>> > function for whole kmem. If that one needs to do tcp kmem specific
>
>> > cleanup then it should be done inside kmem_cgroup_css_offline.
>
>> >
>
>>
>
>> As said in my other mail, for me this makes sense as it is a followup.
>
>>
>
>> But, still I don't know why sock.c has is own mem_cgroup_sockets_{init,destroy}.
>
>
>
> That is the only definition AFAICS (except for !CONFIG_NET where it
>
> expands to NOOP). Please note that memcg_init_kmem is a common kmem
>
> initializator and it needs to be prepared for !CONFIG_NET.
>
>
>
> The same applies to _destroy.
>
> Makes more sense now?
>
>
>
>
So, that stuff comes originally from the net-tree.
No, it all came from tcp kmem accounting. It is a memcg thingy and I
guess it was placed into sock.c because it depends on some static
symbols there (e.g. proto_list_mutex).
>
I understand the !CONFIG_NET case, but lack the understanding why
>
memcontrol.c needs _destroy.
Because it is memcg specific and it has to be called when a group is
destroyed.
>
Can you explain that (sorry /me is no mm-geek)?
>
>
- Sedat -
>
>
[1] http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/net/core/sock.c?id=next-20130703#n147
>
[2] http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/include/net/sock.h?id=next-20130703#n73
>
>
> [...]
>
> --
>
> Michal Hocko
>
> SUSE Labs
--
Michal Hocko
SUSE Labs
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