[RFC,0/2] mm: kmem: optimize obj_cgroup pointer retrieval

Message

Roman Gushchin Dec. 20, 2022, 6:27 p.m. UTC

This patchset improves the performance of get_obj_cgroup_from_current(), which
is used to get an objcg pointer on the kernel memory allocation fast path.

Results (1M 8-bytes accounted allocations):

| version         | accounted (us) | delta | unaccounted (us) |  delta |
|-----------------+----------------+-------+------------------+--------|
| baseline (6.1+) |          81042 |       |            45269 |        |
| patch 1         |          78756 | -2.8% |            42731 |  -5.6% |
| patch 2         |          73650 | -9.1% |            30662 | -32.3% |

Unaccounted allocations were performed from a user's task belonging to
the root cgroup, so savings are particularly large because previously
the root_mem_cgroup pointer was obtained first just to learn that it's
corresponding objcg is NULL.


Roman Gushchin (2):
  mm: kmem: optimize get_obj_cgroup_from_current()
  mm: kmem: add direct objcg pointer to task_struct

 include/linux/sched.h |   4 ++
 mm/memcontrol.c       | 102 ++++++++++++++++++++++++++++++++----------
 2 files changed, 83 insertions(+), 23 deletions(-)