bpf: Optimize call_rcu in non-preallocated hash map.

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Doing call_rcu() million times a second becomes a bottle neck.
Convert non-preallocated hash map from call_rcu to SLAB_TYPESAFE_BY_RCU.
The rcu critical section is no longer observed for one htab element
which makes non-preallocated hash map behave just like preallocated hash map.
The map elements are released back to kernel memory after observing
rcu critical section.
This improves 'map_perf_test 4' performance from 100k events per second
to 250k events per second.

bpf_mem_alloc + percpu_counter + typesafe_by_rcu provide 10x performance
boost to non-preallocated hash map and make it within few % of preallocated map
while consuming fraction of memory.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220902211058.60789-8-alexei.starovoitov@gmail.com

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Alexei Starovoitov 2022-09-02 14:10:49 -07:00 • committed by Daniel Borkmann

parent 86fe28f769

commit 0fd7c5d433

3 changed files with 7 additions and 14 deletions

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8

kernel/bpf/hashtab.c

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2

kernel/bpf/memalloc.c

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11

tools/testing/selftests/bpf/progs/timer.c

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