[bpf-next,v2,0/6] bpf: Reduce memory usage for bpf_global_percpu_ma

Message

Yonghong Song Dec. 15, 2023, 12:11 a.m. UTC

Currently when a bpf program intends to allocate memory for percpu kptr,
the verifier will call bpf_mem_alloc_init() to prefill all supported
unit sizes and this caused memory consumption very big for large number
of cpus. For example, for 128-cpu system, the total memory consumption
with initial prefill is ~175MB. Things will become worse for systems
with even more cpus.

Patch 1 is a preparatory patch.
Patch 2 avoids unnecessary extra percpu memory allocation.
Patch 3 addresses memory consumption issue by avoiding to prefill
with all unit sizes, i.e. only prefilling with user specified size.
Patch 4 further reduces memory consumption by limiting the
number of prefill entries for percpu memory allocation.
Patch 5 rejects percpu memory allocation with bpf_global_percpu_ma
when allocation size is greater than 512 bytes.
Patch 6 fixed one test due to Patch 5 and added one test to
show the verification failure log message.

Changelogs:
  v1 -> v2:
    . Avoid unnecessary extra percpu memory allocation.
    . Add a separate function to do bpf_global_percpu_ma initialization
    . promote.
    . Promote function static 'sizes' array to file static.
    . Add comments to explain to refill only one item for percpu alloc.

Yonghong Song (6):
  bpf: Refactor to have a memalloc cache destroying function
  bpf: Avoid unnecessary extra percpu memory allocation
  bpf: Allow per unit prefill for non-fix-size percpu memory allocator
  bpf: Refill only one percpu element in memalloc
  bpf: Limit up to 512 bytes for bpf_global_percpu_ma allocation
  selftests/bpf: Cope with 512 bytes limit with bpf_global_percpu_ma

 include/linux/bpf.h                           |   2 +-
 include/linux/bpf_mem_alloc.h                 |   7 ++
 kernel/bpf/core.c                             |   8 +-
 kernel/bpf/memalloc.c                         | 100 +++++++++++++++---
 kernel/bpf/verifier.c                         |  36 ++++---
 .../selftests/bpf/progs/percpu_alloc_fail.c   |  18 ++++
 .../testing/selftests/bpf/progs/test_bpf_ma.c |   9 --
 7 files changed, 138 insertions(+), 42 deletions(-)