On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@xxxxxx> wrote: > > This is v6 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. Is this based on just SLUB or does this have a similar impact on SLAB as well? > The reduced number of unmovable slab pages should also have a positive > effect on the memory fragmentation. That would be awesome. We have seen fragmentation getting very bad on system (or node) level memory pressure. Is that the same for you? > > 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. > Have you performed any [perf] testing on SLAB with this patchset? > v6: > 1) rebased on top of the mm tree > 2) removed a redundant check from cache_from_obj(), suggested by Vlastimil > > v5: > 1) fixed a build error, spotted by Vlastimil > 2) added a comment about memcg->nr_charged_bytes, asked by Johannes > 3) added missed acks and reviews > > 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 | 85 ++- > 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 | 608 +++++++++++-------- > mm/oom_kill.c | 2 +- > mm/page_alloc.c | 8 +- > mm/slab.c | 70 +-- > mm/slab.h | 372 +++++------- > 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, 1374 insertions(+), 1405 deletions(-) > create mode 100755 tools/cgroup/memcg_slabinfo.py > create mode 100644 tools/testing/selftests/cgroup/test_kmem.c > > -- > 2.25.4 >
