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Date: Tue, 2 Mar 2021 10:50:04 +0800
From: Muchun Song <songmuchun@...edance.com>
To: Roman Gushchin <guro@...com>
Cc: viro@...iv.linux.org.uk, Jan Kara <jack@...e.cz>,
amir73il@...il.com, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, andrii@...nel.org,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>, kpsingh@...nel.org,
mingo@...hat.com, Peter Zijlstra <peterz@...radead.org>,
juri.lelli@...hat.com,
Vincent Guittot <vincent.guittot@...aro.org>,
dietmar.eggemann@....com, Steven Rostedt <rostedt@...dmis.org>,
Benjamin Segall <bsegall@...gle.com>, mgorman@...e.de,
bristot@...hat.com, Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Shakeel Butt <shakeelb@...gle.com>,
Alex Shi <alex.shi@...ux.alibaba.com>,
Chris Down <chris@...isdown.name>, richard.weiyang@...il.com,
Vlastimil Babka <vbabka@...e.cz>,
mathieu.desnoyers@...icios.com, posk@...gle.com,
Jann Horn <jannh@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Daniel Vetter <daniel.vetter@...ll.ch>, longman@...hat.com,
Michel Lespinasse <walken@...gle.com>,
Christian Brauner <christian.brauner@...ntu.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Kees Cook <keescook@...omium.org>, krisman@...labora.com,
esyr@...hat.com, Suren Baghdasaryan <surenb@...gle.com>,
Marco Elver <elver@...gle.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
Cgroups <cgroups@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Xiongchun duan <duanxiongchun@...edance.com>
Subject: Re: [External] Re: [PATCH 0/5] Use obj_cgroup APIs to change kmem pages
On Tue, Mar 2, 2021 at 9:12 AM Roman Gushchin <guro@...com> wrote:
>
> Hi Muchun!
>
> On Mon, Mar 01, 2021 at 02:22:22PM +0800, Muchun Song wrote:
> > Since Roman series "The new cgroup slab memory controller" applied. All
> > slab objects are changed via the new APIs of obj_cgroup. This new APIs
> > introduce a struct obj_cgroup instead of using struct mem_cgroup directly
> > to charge slab objects. It prevents long-living objects from pinning the
> > original memory cgroup in the memory. But there are still some corner
> > objects (e.g. allocations larger than order-1 page on SLUB) which are
> > not charged via the API of obj_cgroup. Those objects (include the pages
> > which are allocated from buddy allocator directly) are charged as kmem
> > pages which still hold a reference to the memory cgroup.
>
> Yes, this is a good idea, large kmallocs should be treated the same
> way as small ones.
>
> >
> > E.g. We know that the kernel stack is charged as kmem pages because the
> > size of the kernel stack can be greater than 2 pages (e.g. 16KB on x86_64
> > or arm64). If we create a thread (suppose the thread stack is charged to
> > memory cgroup A) and then move it from memory cgroup A to memory cgroup
> > B. Because the kernel stack of the thread hold a reference to the memory
> > cgroup A. The thread can pin the memory cgroup A in the memory even if
> > we remove the cgroup A. If we want to see this scenario by using the
> > following script. We can see that the system has added 500 dying cgroups.
> >
> > #!/bin/bash
> >
> > cat /proc/cgroups | grep memory
> >
> > cd /sys/fs/cgroup/memory
> > echo 1 > memory.move_charge_at_immigrate
> >
> > for i in range{1..500}
> > do
> > mkdir kmem_test
> > echo $$ > kmem_test/cgroup.procs
> > sleep 3600 &
> > echo $$ > cgroup.procs
> > echo `cat kmem_test/cgroup.procs` > cgroup.procs
> > rmdir kmem_test
> > done
> >
> > cat /proc/cgroups | grep memory
>
> Well, moving processes between cgroups always created a lot of issues
> and corner cases and this one is definitely not the worst. So this problem
> looks a bit artificial, unless I'm missing something. But if it doesn't
> introduce any new performance costs and doesn't make the code more complex,
> I have nothing against.
OK. I just want to show that large kmallocs are charged as kmem pages.
So I constructed this test case.
>
> Btw, can you, please, run the spell-checker on commit logs? There are many
> typos (starting from the title of the series, I guess), which make the patchset
> look less appealing.
Sorry for my poor English. I will do that. Thanks for your suggestions.
>
> Thank you!
>
> >
> > This patchset aims to make those kmem pages drop the reference to memory
> > cgroup by using the APIs of obj_cgroup. Finally, we can see that the number
> > of the dying cgroups will not increase if we run the above test script.
> >
> > Patch 1-3 are using obj_cgroup APIs to charge kmem pages. The remote
> > memory cgroup charing APIs is a mechanism to charge kernel memory to a
> > given memory cgroup. So I also make it use the APIs of obj_cgroup.
> > Patch 4-5 are doing this.
> >
> > Muchun Song (5):
> > mm: memcontrol: introduce obj_cgroup_{un}charge_page
> > mm: memcontrol: make page_memcg{_rcu} only applicable for non-kmem
> > page
> > mm: memcontrol: reparent the kmem pages on cgroup removal
> > mm: memcontrol: move remote memcg charging APIs to CONFIG_MEMCG_KMEM
> > mm: memcontrol: use object cgroup for remote memory cgroup charging
> >
> > fs/buffer.c | 10 +-
> > fs/notify/fanotify/fanotify.c | 6 +-
> > fs/notify/fanotify/fanotify_user.c | 2 +-
> > fs/notify/group.c | 3 +-
> > fs/notify/inotify/inotify_fsnotify.c | 8 +-
> > fs/notify/inotify/inotify_user.c | 2 +-
> > include/linux/bpf.h | 2 +-
> > include/linux/fsnotify_backend.h | 2 +-
> > include/linux/memcontrol.h | 109 +++++++++++---
> > include/linux/sched.h | 6 +-
> > include/linux/sched/mm.h | 30 ++--
> > kernel/bpf/syscall.c | 35 ++---
> > kernel/fork.c | 4 +-
> > mm/memcontrol.c | 276 ++++++++++++++++++++++-------------
> > mm/page_alloc.c | 4 +-
> > 15 files changed, 324 insertions(+), 175 deletions(-)
> >
> > --
> > 2.11.0
> >
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