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Yonghong Song says:
====================
bpf: Reduce memory usage for bpf_global_percpu_ma
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 has much smaller low/high watermarks for percpu allocation
to reduce memory consumption.
Patch 6 rejects percpu memory allocation with bpf_global_percpu_ma
when allocation size is greater than 512 bytes.
Patch 7 fixed test_bpf_ma test due to Patch 5.
Patch 8 added one test to show the verification failure log message.
Changelogs:
v5 -> v6:
. Change bpf_mem_alloc_percpu_init() to add objcg as one of parameters.
For bpf_global_percpu_ma, the objcg is NULL, corresponding root memcg.
v4 -> v5:
. Do not do bpf_global_percpu_ma initialization at init stage, instead
doing initialization when the verifier knows it is going to be used
by bpf prog.
. Using much smaller low/high watermarks for percpu allocation.
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.
====================
Link: https://lore.kernel.org/r/20231222031729.1287957-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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