Re: [External] Re: [RFC PATCH v3 00/12] Use obj_cgroup APIs to charge the LRU pages

[Muchun Song]

On Tue, May 18, 2021 at 10:17 PM Roman Gushchin <guro@xxxxxx> wrote:
>
> 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.

Waiting on your review. Thanks Roman.

>
> Thanks!
>
> Sent from my iPhone
>
> > On May 18, 2021, at 06:50, Muchun Song <songmuchun@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx/
> >> [2] https://lore.kernel.org/linux-mm/20200623015846.1141975-1-guro@xxxxxx/
> >> [3] https://lore.kernel.org/linux-mm/20210319163821.20704-1-songmuchun@xxxxxxxxxxxxx/
> >>
> >> 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
> >>