[PATCH v4 00/19] The new cgroup slab memory controller

Roman Gushchin
2020-05-26T21:42:39Z

This is a fourth version of the slab cgroup controller rework.

The patchset moves the accounting from the page level to the object
level. It allows to share slab pages between memory cgroups.
This leads to a significant win in the slab utilization (up to 45%)
and the corresponding drop in the total kernel memory footprint.
The reduced number of unmovable slab pages should also have a positive
effect on the memory fragmentation.

The patchset makes the slab accounting code simpler: there is no more
need in the complicated dynamic creation and destruction of per-cgroup
slab caches, all memory cgroups use a global set of shared slab caches.
The lifetime of slab caches is not more connected to the lifetime
of memory cgroups.

The more precise accounting does require more CPU, however in practice
the difference seems to be negligible. We've been using the new slab
controller in Facebook production for several months with different
workloads and haven't seen any noticeable regressions. What we've seen
were memory savings in order of 1 GB per host (it varied heavily depending
on the actual workload, size of RAM, number of CPUs, memory pressure, etc).

The third version of the patchset added yet another step towards
the simplification of the code: sharing of slab caches between
accounted and non-accounted allocations. It comes with significant
upsides (most noticeable, a complete elimination of dynamic slab caches
creation) but not without some regression risks, so this change sits
on top of the patchset and is not completely merged in. So in the unlikely
event of a noticeable performance regression it can be reverted separately.

v4:
1) rebased on top of the mm tree, some fixes here and there
2) merged obj_to_index() with slab_index(), suggested by Vlastimil
3) changed objects_per_slab() to a better objects_per_slab_page(),
suggested by Vlastimil
4) other minor fixes and changes

v3:
1) added a patch that switches to a global single set of kmem_caches
2) kmem API clean up dropped, because if has been already merged
3) byte-sized slab vmstat API over page-sized global counters and
bytes-sized memcg/lruvec counters
3) obj_cgroup refcounting simplifications and other minor fixes
4) other minor changes

v2:
1) implemented re-layering and renaming suggested by Johannes,
added his patch to the set. Thanks!
2) fixed the issue discovered by Bharata B Rao. Thanks!
3) added kmem API clean up part
4) added slab/memcg follow-up clean up part
5) fixed a couple of issues discovered by internal testing on FB fleet.
6) added kselftests
7) included metadata into the charge calculation
8) refreshed commit logs, regrouped patches, rebased onto mm tree, etc

v1:
1) fixed a bug in zoneinfo_show_print()
2) added some comments to the subpage charging API, a minor fix
3) separated memory.kmem.slabinfo deprecation into a separate patch,
provided a drgn-based replacement
4) rebased on top of the current mm tree

RFC:
https://lwn.net/Articles/798605/

Johannes Weiner (1):
mm: memcontrol: decouple reference counting from page accounting

Roman Gushchin (18):
mm: memcg: factor out memcg- and lruvec-level changes out of
__mod_lruvec_state()
mm: memcg: prepare for byte-sized vmstat items
mm: memcg: convert vmstat slab counters to bytes
mm: slub: implement SLUB version of obj_to_index()
mm: memcg/slab: obj_cgroup API
mm: memcg/slab: allocate obj_cgroups for non-root slab pages
mm: memcg/slab: save obj_cgroup for non-root slab objects
mm: memcg/slab: charge individual slab objects instead of pages
mm: memcg/slab: deprecate memory.kmem.slabinfo
mm: memcg/slab: move memcg_kmem_bypass() to memcontrol.h
mm: memcg/slab: use a single set of kmem_caches for all accounted
allocations
mm: memcg/slab: simplify memcg cache creation
mm: memcg/slab: remove memcg_kmem_get_cache()
mm: memcg/slab: deprecate slab_root_caches
mm: memcg/slab: remove redundant check in memcg_accumulate_slabinfo()
mm: memcg/slab: use a single set of kmem_caches for all allocations
kselftests: cgroup: add kernel memory accounting tests
tools/cgroup: add memcg_slabinfo.py tool

drivers/base/node.c | 6 +-
fs/proc/meminfo.c | 4 +-
include/linux/memcontrol.h | 80 ++-
include/linux/mm_types.h | 5 +-
include/linux/mmzone.h | 24 +-
include/linux/slab.h | 5 -
include/linux/slab_def.h | 9 +-
include/linux/slub_def.h | 31 +-
include/linux/vmstat.h | 14 +-
kernel/power/snapshot.c | 2 +-
mm/memcontrol.c | 593 +++++++++++--------
mm/oom_kill.c | 2 +-
mm/page_alloc.c | 8 +-
mm/slab.c | 70 +--
mm/slab.h | 365 +++++-------
mm/slab_common.c | 643 +--------------------
mm/slob.c | 12 +-
mm/slub.c | 229 +-------
mm/vmscan.c | 3 +-
mm/vmstat.c | 30 +-
mm/workingset.c | 6 +-
tools/cgroup/memcg_slabinfo.py | 226 ++++++++
tools/testing/selftests/cgroup/.gitignore | 1 +
tools/testing/selftests/cgroup/Makefile | 2 +
tools/testing/selftests/cgroup/test_kmem.c | 382 ++++++++++++
25 files changed, 1359 insertions(+), 1393 deletions(-)
create mode 100755 tools/cgroup/memcg_slabinfo.py
create mode 100644 tools/testing/selftests/cgroup/test_kmem.c

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2.25.4