| Message ID | 20250320114200.14377-1-jolsa@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | uprobes: Add support to optimize usdt probes on x86_64 | expand |
On 03/20, Jiri Olsa wrote: > > hi, > this patchset adds support to optimize usdt probes on top of 5-byte > nop instruction. Just in case... This series conflicts with (imo very important) changes from David, [PATCH v2 0/3] kernel/events/uprobes: uprobe_write_opcode() rewrite https://lore.kernel.org/all/20250318221457.3055598-1-david@redhat.com/ I think they should be merged first. (and I am not sure yet, but it seems that we should cleanup (fix?) the update_ref_ctr() logic before other changes). Oleg.
On Thu, Mar 20, 2025 at 01:23:44PM +0100, Oleg Nesterov wrote: > On 03/20, Jiri Olsa wrote: > > > > hi, > > this patchset adds support to optimize usdt probes on top of 5-byte > > nop instruction. > > Just in case... This series conflicts with (imo very important) changes > from David, > > [PATCH v2 0/3] kernel/events/uprobes: uprobe_write_opcode() rewrite > https://lore.kernel.org/all/20250318221457.3055598-1-david@redhat.com/ > > I think they should be merged first. ok, I'll check on those thanks, jirka > > (and I am not sure yet, but it seems that we should cleanup (fix?) the > update_ref_ctr() logic before other changes). > > Oleg. >
hi, this patchset adds support to optimize usdt probes on top of 5-byte nop instruction. The generic approach (optimize all uprobes) is hard due to emulating possible multiple original instructions and its related issues. The usdt case, which stores 5-byte nop seems much easier, so starting with that. The basic idea is to replace breakpoint exception with syscall which is faster on x86_64. For more details please see changelog of patch 8. The run_bench_uprobes.sh benchmark triggers uprobe (on top of different original instructions) in a loop and counts how many of those happened per second (the unit below is million loops). There's big speed up if you consider current usdt implementation (uprobe-nop) compared to proposed usdt (uprobe-nop5): current: usermode-count : 152.604 ± 0.044M/s syscall-count : 13.359 ± 0.042M/s --> uprobe-nop : 3.229 ± 0.002M/s uprobe-push : 3.086 ± 0.004M/s uprobe-ret : 1.114 ± 0.004M/s uprobe-nop5 : 1.121 ± 0.005M/s uretprobe-nop : 2.145 ± 0.002M/s uretprobe-push : 2.070 ± 0.001M/s uretprobe-ret : 0.931 ± 0.001M/s uretprobe-nop5 : 0.957 ± 0.001M/s after the change: usermode-count : 152.448 ± 0.244M/s syscall-count : 14.321 ± 0.059M/s uprobe-nop : 3.148 ± 0.007M/s uprobe-push : 2.976 ± 0.004M/s uprobe-ret : 1.068 ± 0.003M/s --> uprobe-nop5 : 7.038 ± 0.007M/s uretprobe-nop : 2.109 ± 0.004M/s uretprobe-push : 2.035 ± 0.001M/s uretprobe-ret : 0.908 ± 0.001M/s uretprobe-nop5 : 3.377 ± 0.009M/s I see bit more speed up on Intel (above) compared to AMD. The big nop5 speed up is partly due to emulating nop5 and partly due to optimization. The key speed up we do this for is the USDT switch from nop to nop5: uprobe-nop : 3.148 ± 0.007M/s uprobe-nop5 : 7.038 ± 0.007M/s rfc v3 changes: - I tried to have just single syscall for both entry and return uprobe, but it turned out to be slower than having two separated syscalls, probably due to extra save/restore processing we have to do for argument reg, I see differences like: 2 syscalls: uprobe-nop5 : 7.038 ± 0.007M/s 1 syscall: uprobe-nop5 : 6.943 ± 0.003M/s - use instructions (nop5/int3/call) to determine the state of the uprobe update in the process - removed endbr instruction from uprobe trampoline - seccomp changes pending todo (or follow ups): - shadow stack fails for uprobe session setup, will fix it in next version - use PROCMAP_QUERY in tests - alloc 'struct uprobes_state' for mm_struct only when needed [Andrii] thanks, jirka Cc: Eyal Birger <eyal.birger@gmail.com> Cc: kees@kernel.org --- Jiri Olsa (23): uprobes: Rename arch_uretprobe_trampoline function uprobes: Make copy_from_page global uprobes: Move ref_ctr_offset update out of uprobe_write_opcode uprobes: Add uprobe_write function uprobes: Add nbytes argument to uprobe_write_opcode uprobes: Add orig argument to uprobe_write and uprobe_write_opcode uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock uprobes/x86: Add uprobe syscall to speed up uprobe uprobes/x86: Add mapping for optimized uprobe trampolines uprobes/x86: Add support to emulate nop5 instruction uprobes/x86: Add support to optimize uprobes selftests/bpf: Use 5-byte nop for x86 usdt probes selftests/bpf: Reorg the uprobe_syscall test function selftests/bpf: Rename uprobe_syscall_executed prog to test_uretprobe_multi selftests/bpf: Add uprobe/usdt syscall tests selftests/bpf: Add hit/attach/detach race optimized uprobe test selftests/bpf: Add uprobe syscall sigill signal test selftests/bpf: Add optimized usdt variant for basic usdt test selftests/bpf: Add uprobe_regs_equal test selftests/bpf: Change test_uretprobe_regs_change for uprobe and uretprobe selftests/bpf: Add 5-byte nop uprobe trigger bench seccomp: passthrough uprobe systemcall without filtering selftests/seccomp: validate uprobe syscall passes through seccomp arch/arm/probes/uprobes/core.c | 2 +- arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/x86/include/asm/uprobes.h | 7 ++ arch/x86/kernel/uprobes.c | 540 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- include/linux/syscalls.h | 2 + include/linux/uprobes.h | 19 +++- kernel/events/uprobes.c | 141 +++++++++++++++++------- kernel/fork.c | 1 + kernel/seccomp.c | 32 ++++-- kernel/sys_ni.c | 1 + tools/testing/selftests/bpf/bench.c | 12 +++ tools/testing/selftests/bpf/benchs/bench_trigger.c | 42 ++++++++ tools/testing/selftests/bpf/benchs/run_bench_uprobes.sh | 2 +- tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c | 453 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------ tools/testing/selftests/bpf/prog_tests/usdt.c | 38 ++++--- tools/testing/selftests/bpf/progs/uprobe_syscall.c | 4 +- tools/testing/selftests/bpf/progs/uprobe_syscall_executed.c | 41 ++++++- tools/testing/selftests/bpf/sdt.h | 9 +- tools/testing/selftests/bpf/test_kmods/bpf_testmod.c | 11 +- tools/testing/selftests/seccomp/seccomp_bpf.c | 107 ++++++++++++++---- 20 files changed, 1338 insertions(+), 127 deletions(-)