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Date: Tue, 18 May 2021 14:17:03 +0000
From: Roman Gushchin <guro@...com>
To: Muchun Song <songmuchun@...edance.com>
CC: Johannes Weiner <hannes@...xchg.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
Shakeel Butt <shakeelb@...gle.com>,
Xiongchun duan <duanxiongchun@...edance.com>,
"fam.zheng@...edance.com" <fam.zheng@...edance.com>,
"Singh, Balbir" <bsingharora@...il.com>,
Yang Shi <shy828301@...il.com>,
Alex Shi <alex.shi@...ux.alibaba.com>,
Michal Hocko <mhocko@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH v3 00/12] Use obj_cgroup APIs to charge the LRU pages
Hi Muchun!
It looks like the writeback problem will be solved in a different way, which will not require generalization of the obj_cgroup api to the cgroup level. It’s not fully confirmed yet though. We still might wanna do this generalization lingn-term, but as now I have no objections for continuing the work on your patchset. I’m on pto this week, but will take a deeper look at your patches early next week. Sorry for the delay.
Thanks!
Sent from my iPhone
> On May 18, 2021, at 06:50, Muchun Song <songmuchun@...edance.com> wrote:
>
> Ping...
>
> Hi Johannes and Roman,
>
> Any suggestions on this patch set?
>
> Thanks.
>
>> On Wed, Apr 21, 2021 at 3:01 PM Muchun Song <songmuchun@...edance.com> wrote:
>>
>> This is v3 based on the top of the series[1] (memcontrol code cleanup and
>> simplification). Roman is working on the generalization of obj_cgroup API.
>> But before that, hope someone can review this patches for correctness.
>>
>> Since the following patchsets applied. All the kernel memory are charged
>> with the new APIs of obj_cgroup.
>>
>> [v17,00/19] The new cgroup slab memory controller[2]
>> [v5,0/7] Use obj_cgroup APIs to charge kmem pages[3]
>>
>> But user memory allocations (LRU pages) pinning memcgs for a long time -
>> it exists at a larger scale and is causing recurring problems in the real
>> world: page cache doesn't get reclaimed for a long time, or is used by the
>> second, third, fourth, ... instance of the same job that was restarted into
>> a new cgroup every time. Unreclaimable dying cgroups pile up, waste memory,
>> and make page reclaim very inefficient.
>>
>> We can convert LRU pages and most other raw memcg pins to the objcg direction
>> to fix this problem, and then the LRU pages will not pin the memcgs.
>>
>> This patchset aims to make the LRU pages to 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 following test script.
>>
>> ```bash
>> #!/bin/bash
>>
>> cat /proc/cgroups | grep memory
>>
>> cd /sys/fs/cgroup/memory
>>
>> for i in range{1..500}
>> do
>> mkdir test
>> echo $$ > test/cgroup.procs
>> sleep 60 &
>> echo $$ > cgroup.procs
>> echo `cat test/cgroup.procs` > cgroup.procs
>> rmdir test
>> done
>>
>> cat /proc/cgroups | grep memory
>> ```
>>
>> Thanks.
>>
>> [1] https://lore.kernel.org/linux-mm/20210417043538.9793-1-songmuchun@bytedance.com/
>> [2] https://lore.kernel.org/linux-mm/20200623015846.1141975-1-guro@fb.com/
>> [3] https://lore.kernel.org/linux-mm/20210319163821.20704-1-songmuchun@bytedance.com/
>>
>> Changlogs in RFC v3:
>> 1. Drop the code cleanup and simplification patches. Gather those patches
>> into a separate series[1].
>> 2. Rework patch #1 suggested by Johannes.
>>
>> Changlogs in RFC v2:
>> 1. Collect Acked-by tags by Johannes. Thanks.
>> 2. Rework lruvec_holds_page_lru_lock() suggested by Johannes. Thanks.
>> 3. Fix move_pages_to_lru().
>>
>> Muchun Song (12):
>> mm: memcontrol: move the objcg infrastructure out of CONFIG_MEMCG_KMEM
>> mm: memcontrol: introduce compact_lock_page_lruvec_irqsave
>> mm: memcontrol: make lruvec lock safe when the LRU pages reparented
>> mm: vmscan: rework move_pages_to_lru()
>> mm: thp: introduce lock/unlock_split_queue{_irqsave}()
>> mm: thp: make deferred split queue lock safe when the LRU pages
>> reparented
>> mm: memcontrol: make all the callers of page_memcg() safe
>> mm: memcontrol: introduce memcg_reparent_ops
>> mm: memcontrol: use obj_cgroup APIs to charge the LRU pages
>> mm: memcontrol: rename {un}lock_page_memcg() to {un}lock_page_objcg()
>> mm: lru: add VM_BUG_ON_PAGE to lru maintenance function
>> mm: lru: use lruvec lock to serialize memcg changes
>>
>> Documentation/admin-guide/cgroup-v1/memory.rst | 2 +-
>> fs/buffer.c | 13 +-
>> fs/fs-writeback.c | 23 +-
>> fs/iomap/buffered-io.c | 4 +-
>> include/linux/memcontrol.h | 182 ++++----
>> include/linux/mm_inline.h | 6 +
>> mm/compaction.c | 36 +-
>> mm/filemap.c | 2 +-
>> mm/huge_memory.c | 171 ++++++--
>> mm/memcontrol.c | 562 ++++++++++++++++++-------
>> mm/migrate.c | 4 +
>> mm/page-writeback.c | 24 +-
>> mm/page_io.c | 5 +-
>> mm/rmap.c | 14 +-
>> mm/swap.c | 46 +-
>> mm/vmscan.c | 56 ++-
>> 16 files changed, 795 insertions(+), 355 deletions(-)
>>
>> --
>> 2.11.0
>>
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