For now, the budget of the hash table that is used for fprobe_ip_table is fixed, which is 256, and can cause huge overhead when the hooked functions is a huge quantity.
In this series, we use rhltable for fprobe_ip_table to reduce the overhead. Meanwhile, we also add the benchmark testcase "kprobe-multi-all" and, which will hook all the kernel functions during the testing. Before this series, the performance is: usermode-count : 889.269 ± 0.053M/s kernel-count : 437.149 ± 0.501M/s syscall-count : 31.618 ± 0.725M/s fentry : 135.591 ± 0.129M/s fexit : 68.127 ± 0.062M/s fmodret : 71.764 ± 0.098M/s rawtp : 198.375 ± 0.190M/s tp : 79.770 ± 0.064M/s kprobe : 54.590 ± 0.021M/s kprobe-multi : 57.940 ± 0.044M/s kprobe-multi-all: 12.151 ± 0.020M/s kretprobe : 21.945 ± 0.163M/s kretprobe-multi: 28.199 ± 0.018M/s kretprobe-multi-all: 9.667 ± 0.008M/s With this series, the performance is: usermode-count : 888.863 ± 0.378M/s kernel-count : 429.339 ± 0.136M/s syscall-count : 31.215 ± 0.019M/s fentry : 135.604 ± 0.118M/s fexit : 68.470 ± 0.074M/s fmodret : 70.957 ± 0.016M/s rawtp : 202.650 ± 0.304M/s tp : 80.428 ± 0.053M/s kprobe : 55.915 ± 0.074M/s kprobe-multi : 54.015 ± 0.039M/s kprobe-multi-all: 46.381 ± 0.024M/s kretprobe : 22.234 ± 0.050M/s kretprobe-multi: 27.946 ± 0.016M/s kretprobe-multi-all: 24.439 ± 0.016M/s The benchmark of "kprobe-multi-all" increase from 12.151M/s to 46.381M/s. I don't know why, but the benchmark result for "kprobe-multi-all" is much better in this version for the legacy case(without this series). In V2, the benchmark increase from 6.283M/s to 54.487M/s, but it become 12.151M/s to 46.381M/s in this version. Maybe it has some relation with the compiler optimization :/ The result of this version should be more accurate, which is similar to Jiri's result: from 3.565 ± 0.047M/s to 11.553 ± 0.458M/s. The locking is not handled properly in the first patch. In the fprobe_entry, we should use RCU when we access the rhlist_head. However, we can't use RCU for __fprobe_handler, as it can sleep. In the origin logic, it seems that the usage of hlist_for_each_entry_from_rcu() is not protected by rcu_read_lock neither, isn't it? I don't know how to handle this part ;( Changes since V2: * some format optimization, and handle the error that returned from rhltable_insert in insert_fprobe_node for the 1st patch * add "kretprobe-multi-all" testcase to the 4th patch * attach a empty kprobe-multi prog to the kernel functions, which don't call incr_count(), to make the result more accurate in the 4th patch Changes Since V1: * use rhltable instead of rhashtable to handle the duplicate key. Menglong Dong (4): fprobe: use rhltable for fprobe_ip_table selftests/bpf: move get_ksyms and get_addrs to trace_helpers.c selftests/bpf: skip recursive functions for kprobe_multi selftests/bpf: add benchmark testing for kprobe-multi-all include/linux/fprobe.h | 2 +- kernel/trace/fprobe.c | 155 +++++++----- tools/testing/selftests/bpf/bench.c | 4 + .../selftests/bpf/benchs/bench_trigger.c | 54 ++++ .../selftests/bpf/benchs/run_bench_trigger.sh | 4 +- .../bpf/prog_tests/kprobe_multi_test.c | 220 +---------------- .../selftests/bpf/progs/trigger_bench.c | 12 + tools/testing/selftests/bpf/trace_helpers.c | 233 ++++++++++++++++++ tools/testing/selftests/bpf/trace_helpers.h | 3 + 9 files changed, 401 insertions(+), 286 deletions(-) -- 2.50.1
