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# 68bc61c2 07-Feb-2024 Marco Elver <[email protected]>

bpf: Allow compiler to inline most of bpf_local_storage_lookup()

In various performance profiles of kernels with BPF programs attached,
bpf_local_storage_lookup() appears as a significant portion of

bpf: Allow compiler to inline most of bpf_local_storage_lookup()

In various performance profiles of kernels with BPF programs attached,
bpf_local_storage_lookup() appears as a significant portion of CPU
cycles spent. To enable the compiler generate more optimal code, turn
bpf_local_storage_lookup() into a static inline function, where only the
cache insertion code path is outlined

Notably, outlining cache insertion helps avoid bloating callers by
duplicating setting up calls to raw_spin_{lock,unlock}_irqsave() (on
architectures which do not inline spin_lock/unlock, such as x86), which
would cause the compiler produce worse code by deciding to outline
otherwise inlinable functions. The call overhead is neutral, because we
make 2 calls either way: either calling raw_spin_lock_irqsave() and
raw_spin_unlock_irqsave(); or call __bpf_local_storage_insert_cache(),
which calls raw_spin_lock_irqsave(), followed by a tail-call to
raw_spin_unlock_irqsave() where the compiler can perform TCO and (in
optimized uninstrumented builds) turns it into a plain jump. The call to
__bpf_local_storage_insert_cache() can be elided entirely if
cacheit_lockit is a false constant expression.

Based on results from './benchs/run_bench_local_storage.sh' (21 trials,
reboot between each trial; x86 defconfig + BPF, clang 16) this produces
improvements in throughput and latency in the majority of cases, with an
average (geomean) improvement of 8%:

+---- Hashmap Control --------------------
|
| + num keys: 10
| : <before> | <after>
| +-+ hashmap (control) sequential get +----------------------+----------------------
| +- hits throughput | 14.789 M ops/s | 14.745 M ops/s ( ~ )
| +- hits latency | 67.679 ns/op | 67.879 ns/op ( ~ )
| +- important_hits throughput | 14.789 M ops/s | 14.745 M ops/s ( ~ )
|
| + num keys: 1000
| : <before> | <after>
| +-+ hashmap (control) sequential get +----------------------+----------------------
| +- hits throughput | 12.233 M ops/s | 12.170 M ops/s ( ~ )
| +- hits latency | 81.754 ns/op | 82.185 ns/op ( ~ )
| +- important_hits throughput | 12.233 M ops/s | 12.170 M ops/s ( ~ )
|
| + num keys: 10000
| : <before> | <after>
| +-+ hashmap (control) sequential get +----------------------+----------------------
| +- hits throughput | 7.220 M ops/s | 7.204 M ops/s ( ~ )
| +- hits latency | 138.522 ns/op | 138.842 ns/op ( ~ )
| +- important_hits throughput | 7.220 M ops/s | 7.204 M ops/s ( ~ )
|
| + num keys: 100000
| : <before> | <after>
| +-+ hashmap (control) sequential get +----------------------+----------------------
| +- hits throughput | 5.061 M ops/s | 5.165 M ops/s (+2.1%)
| +- hits latency | 198.483 ns/op | 194.270 ns/op (-2.1%)
| +- important_hits throughput | 5.061 M ops/s | 5.165 M ops/s (+2.1%)
|
| + num keys: 4194304
| : <before> | <after>
| +-+ hashmap (control) sequential get +----------------------+----------------------
| +- hits throughput | 2.864 M ops/s | 2.882 M ops/s ( ~ )
| +- hits latency | 365.220 ns/op | 361.418 ns/op (-1.0%)
| +- important_hits throughput | 2.864 M ops/s | 2.882 M ops/s ( ~ )
|
+---- Local Storage ----------------------
|
| + num_maps: 1
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 33.005 M ops/s | 39.068 M ops/s (+18.4%)
| +- hits latency | 30.300 ns/op | 25.598 ns/op (-15.5%)
| +- important_hits throughput | 33.005 M ops/s | 39.068 M ops/s (+18.4%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 37.151 M ops/s | 44.926 M ops/s (+20.9%)
| +- hits latency | 26.919 ns/op | 22.259 ns/op (-17.3%)
| +- important_hits throughput | 37.151 M ops/s | 44.926 M ops/s (+20.9%)
|
| + num_maps: 10
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 32.288 M ops/s | 38.099 M ops/s (+18.0%)
| +- hits latency | 30.972 ns/op | 26.248 ns/op (-15.3%)
| +- important_hits throughput | 3.229 M ops/s | 3.810 M ops/s (+18.0%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 34.473 M ops/s | 41.145 M ops/s (+19.4%)
| +- hits latency | 29.010 ns/op | 24.307 ns/op (-16.2%)
| +- important_hits throughput | 12.312 M ops/s | 14.695 M ops/s (+19.4%)
|
| + num_maps: 16
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 32.524 M ops/s | 38.341 M ops/s (+17.9%)
| +- hits latency | 30.748 ns/op | 26.083 ns/op (-15.2%)
| +- important_hits throughput | 2.033 M ops/s | 2.396 M ops/s (+17.9%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 34.575 M ops/s | 41.338 M ops/s (+19.6%)
| +- hits latency | 28.925 ns/op | 24.193 ns/op (-16.4%)
| +- important_hits throughput | 11.001 M ops/s | 13.153 M ops/s (+19.6%)
|
| + num_maps: 17
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 28.861 M ops/s | 32.756 M ops/s (+13.5%)
| +- hits latency | 34.649 ns/op | 30.530 ns/op (-11.9%)
| +- important_hits throughput | 1.700 M ops/s | 1.929 M ops/s (+13.5%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 31.529 M ops/s | 36.110 M ops/s (+14.5%)
| +- hits latency | 31.719 ns/op | 27.697 ns/op (-12.7%)
| +- important_hits throughput | 9.598 M ops/s | 10.993 M ops/s (+14.5%)
|
| + num_maps: 24
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 18.602 M ops/s | 19.937 M ops/s (+7.2%)
| +- hits latency | 53.767 ns/op | 50.166 ns/op (-6.7%)
| +- important_hits throughput | 0.776 M ops/s | 0.831 M ops/s (+7.2%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 21.718 M ops/s | 23.332 M ops/s (+7.4%)
| +- hits latency | 46.047 ns/op | 42.865 ns/op (-6.9%)
| +- important_hits throughput | 6.110 M ops/s | 6.564 M ops/s (+7.4%)
|
| + num_maps: 32
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 14.118 M ops/s | 14.626 M ops/s (+3.6%)
| +- hits latency | 70.856 ns/op | 68.381 ns/op (-3.5%)
| +- important_hits throughput | 0.442 M ops/s | 0.458 M ops/s (+3.6%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 17.111 M ops/s | 17.906 M ops/s (+4.6%)
| +- hits latency | 58.451 ns/op | 55.865 ns/op (-4.4%)
| +- important_hits throughput | 4.776 M ops/s | 4.998 M ops/s (+4.6%)
|
| + num_maps: 100
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 5.281 M ops/s | 5.528 M ops/s (+4.7%)
| +- hits latency | 192.398 ns/op | 183.059 ns/op (-4.9%)
| +- important_hits throughput | 0.053 M ops/s | 0.055 M ops/s (+4.9%)
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 6.265 M ops/s | 6.498 M ops/s (+3.7%)
| +- hits latency | 161.436 ns/op | 152.877 ns/op (-5.3%)
| +- important_hits throughput | 1.636 M ops/s | 1.697 M ops/s (+3.7%)
|
| + num_maps: 1000
| : <before> | <after>
| +-+ local_storage cache sequential get +----------------------+----------------------
| +- hits throughput | 0.355 M ops/s | 0.354 M ops/s ( ~ )
| +- hits latency | 2826.538 ns/op | 2827.139 ns/op ( ~ )
| +- important_hits throughput | 0.000 M ops/s | 0.000 M ops/s ( ~ )
| :
| : <before> | <after>
| +-+ local_storage cache interleaved get +----------------------+----------------------
| +- hits throughput | 0.404 M ops/s | 0.403 M ops/s ( ~ )
| +- hits latency | 2481.190 ns/op | 2487.555 ns/op ( ~ )
| +- important_hits throughput | 0.102 M ops/s | 0.101 M ops/s ( ~ )

The on_lookup test in {cgrp,task}_ls_recursion.c is removed
because the bpf_local_storage_lookup is no longer traceable
and adding tracepoint will make the compiler generate worse
code: https://lore.kernel.org/bpf/[email protected]/

Signed-off-by: Marco Elver <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>

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Revision tags: v6.8-rc3, v6.8-rc2, v6.8-rc1, v6.7, v6.7-rc8, v6.7-rc7, v6.7-rc6, v6.7-rc5, v6.7-rc4, v6.7-rc3, v6.7-rc2, v6.7-rc1, v6.6, v6.6-rc7, v6.6-rc6, v6.6-rc5, v6.6-rc4, v6.6-rc3, v6.6-rc2, v6.6-rc1, v6.5, v6.5-rc7, v6.5-rc6, v6.5-rc5, v6.5-rc4, v6.5-rc3, v6.5-rc2, v6.5-rc1, v6.4, v6.4-rc7, v6.4-rc6, v6.4-rc5, v6.4-rc4, v6.4-rc3, v6.4-rc2, v6.4-rc1, v6.3, v6.3-rc7, v6.3-rc6, v6.3-rc5, v6.3-rc4, v6.3-rc3, v6.3-rc2, v6.3-rc1, v6.2, v6.2-rc8, v6.2-rc7, v6.2-rc6, v6.2-rc5, v6.2-rc4, v6.2-rc3, v6.2-rc2, v6.2-rc1, v6.1, v6.1-rc8, v6.1-rc7, v6.1-rc6, v6.1-rc5, v6.1-rc4, v6.1-rc3
# 387b5321 25-Oct-2022 Martin KaFai Lau <[email protected]>

selftests/bpf: Tracing prog can still do lookup under busy lock

This patch modifies the task_ls_recursion test to check that
the first bpf_task_storage_get(&map_a, ...) in BPF_PROG(on_update)
can st

selftests/bpf: Tracing prog can still do lookup under busy lock

This patch modifies the task_ls_recursion test to check that
the first bpf_task_storage_get(&map_a, ...) in BPF_PROG(on_update)
can still do the lockless lookup even it cannot acquire the percpu
busy lock. If the lookup succeeds, it will increment the value
by 1 and the value in the task storage map_a will become 200+1=201.
After that, BPF_PROG(on_update) tries to delete from map_a and
should get -EBUSY because it cannot acquire the percpu busy lock
after finding the data.

Signed-off-by: Martin KaFai Lau <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

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Revision tags: v6.1-rc2, v6.1-rc1, v6.0, v6.0-rc7, v6.0-rc6, v6.0-rc5, v6.0-rc4, v6.0-rc3, v6.0-rc2, v6.0-rc1, v5.19, v5.19-rc8, v5.19-rc7, v5.19-rc6, v5.19-rc5, v5.19-rc4, v5.19-rc3, v5.19-rc2, v5.19-rc1, v5.18, v5.18-rc7, v5.18-rc6, v5.18-rc5, v5.18-rc4, v5.18-rc3, v5.18-rc2, v5.18-rc1, v5.17, v5.17-rc8, v5.17-rc7, v5.17-rc6, v5.17-rc5, v5.17-rc4, v5.17-rc3, v5.17-rc2, v5.17-rc1, v5.16, v5.16-rc8, v5.16-rc7, v5.16-rc6, v5.16-rc5, v5.16-rc4, v5.16-rc3, v5.16-rc2, v5.16-rc1, v5.15, v5.15-rc7, v5.15-rc6, v5.15-rc5, v5.15-rc4, v5.15-rc3, v5.15-rc2, v5.15-rc1, v5.14, v5.14-rc7, v5.14-rc6, v5.14-rc5, v5.14-rc4, v5.14-rc3, v5.14-rc2, v5.14-rc1, v5.13, v5.13-rc7, v5.13-rc6, v5.13-rc5, v5.13-rc4, v5.13-rc3, v5.13-rc2, v5.13-rc1, v5.12, v5.12-rc8, v5.12-rc7, v5.12-rc6, v5.12-rc5, v5.12-rc4, v5.12-rc3, v5.12-rc2, v5.12-rc1, v5.12-rc1-dontuse
# c540957a 25-Feb-2021 Song Liu <[email protected]>

selftests/bpf: Test deadlock from recursive bpf_task_storage_[get|delete]

Add a test with recursive bpf_task_storage_[get|delete] from fentry
programs on bpf_local_storage_lookup and bpf_local_stora

selftests/bpf: Test deadlock from recursive bpf_task_storage_[get|delete]

Add a test with recursive bpf_task_storage_[get|delete] from fentry
programs on bpf_local_storage_lookup and bpf_local_storage_update. Without
proper deadlock prevent mechanism, this test would cause deadlock.

Signed-off-by: Song Liu <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

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