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 avoids unnecessary extra percpu memory allocation.
Patch 2 adds objcg to bpf_mem_alloc at init stage so objcg can be
associated with root cgroup and objcg can be passed to later
bpf_mem_alloc_percpu_unit_init().
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 test_bpf_ma test due to Patch 5.
Patch 7 added one test to show the verification failure log message.
Changelogs:
v3 -> v4:
. Add objcg to bpf_mem_alloc during init stage.
. Initialize objcg at init stage but use it in bpf_mem_alloc_percpu_unit_init().
. Remove check_obj_size() in bpf_mem_alloc_percpu_unit_init().
v2 -> v3:
. Clear the bpf_mem_cache if prefill fails.
. Change test_bpf_ma percpu allocation tests to use bucket_size
as allocation size instead of bucket_size - 8.
. Remove __GFP_ZERO flag from __alloc_percpu_gfp() call.
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 (7):
bpf: Avoid unnecessary extra percpu memory allocation
bpf: Add objcg to bpf_mem_alloc
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
selftests/bpf: Add a selftest with > 512-byte percpu allocation size
include/linux/bpf.h | 2 +-
include/linux/bpf_mem_alloc.h | 8 ++
kernel/bpf/core.c | 8 +-
kernel/bpf/memalloc.c | 90 ++++++++++++++++---
kernel/bpf/verifier.c | 36 ++++----
.../selftests/bpf/prog_tests/test_bpf_ma.c | 20 +++--
.../selftests/bpf/progs/percpu_alloc_fail.c | 18 ++++
.../testing/selftests/bpf/progs/test_bpf_ma.c | 34 +++----
8 files changed, 160 insertions(+), 56 deletions(-)
--
2.34.1
