hi, ping thanks, jirka
On Thu, Jun 05, 2025 at 03:23:27PM +0200, Jiri Olsa wrote: > 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 : 152.501 ± 0.012M/s > syscall-count : 14.463 ± 0.062M/s > --> uprobe-nop : 3.160 ± 0.005M/s > uprobe-push : 3.003 ± 0.003M/s > uprobe-ret : 1.100 ± 0.003M/s > uprobe-nop5 : 3.132 ± 0.012M/s > uretprobe-nop : 2.103 ± 0.002M/s > uretprobe-push : 2.027 ± 0.004M/s > uretprobe-ret : 0.914 ± 0.002M/s > uretprobe-nop5 : 2.115 ± 0.002M/s > > after the change: > usermode-count : 152.343 ± 0.400M/s > syscall-count : 14.851 ± 0.033M/s > uprobe-nop : 3.204 ± 0.005M/s > uprobe-push : 3.040 ± 0.005M/s > uprobe-ret : 1.098 ± 0.003M/s > --> uprobe-nop5 : 7.286 ± 0.017M/s > uretprobe-nop : 2.144 ± 0.001M/s > uretprobe-push : 2.069 ± 0.002M/s > uretprobe-ret : 0.922 ± 0.000M/s > uretprobe-nop5 : 3.487 ± 0.001M/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 : 3.160 ± 0.005M/s > uprobe-nop5 : 7.286 ± 0.017M/s > > > Changes from v2: > - rebased on top of tip/master + mm/mm-stable + 1 extra change [1] > - added acks [Oleg,Andrii] > - more details changelog for patch 1 [Masami] > - several tests changes [Andrii] > - add explicit PAGE_SIZE low limit to vm_unmapped_area call [Andrii] > > > This patchset is adding new syscall, here are notes to check list items > in Documentation/process/adding-syscalls.rst: > > - System Call Alternatives > New syscall seems like the best way in here, because we need > just to quickly enter kernel with no extra arguments processing, > which we'd need to do if we decided to use another syscall. > > - Designing the API: Planning for Extension > The uprobe syscall is very specific and most likely won't be > extended in the future. > > - Designing the API: Other Considerations > N/A because uprobe syscall does not return reference to kernel > object. > > - Proposing the API > Wiring up of the uprobe system call is in separate change, > selftests and man page changes are part of the patchset. > > - Generic System Call Implementation > There's no CONFIG option for the new functionality because it > keeps the same behaviour from the user POV. > > - x86 System Call Implementation > It's 64-bit syscall only. > > - Compatibility System Calls (Generic) > N/A uprobe syscall has no arguments and is not supported > for compat processes. > > - Compatibility System Calls (x86) > N/A uprobe syscall is not supported for compat processes. > > - System Calls Returning Elsewhere > N/A. > > - Other Details > N/A. > > - Testing > Adding new bpf selftests. > > - Man Page > Attached. > > - Do not call System Calls in the Kernel > N/A > > pending todo (or follow ups): > - use PROCMAP_QUERY in tests > - alloc 'struct uprobes_state' for mm_struct only when needed [Andrii] > - use mm_cpumask(vma->vm_mm) in text_poke_sync > > thanks, > jirka > > > Cc: Alejandro Colomar <a...@kernel.org> > Cc: Eyal Birger <eyal.bir...@gmail.com> > Cc: k...@kernel.org > > [1] > https://lore.kernel.org/linux-trace-kernel/20250514101809.2010193-1-jo...@kernel.org/T/#u > --- > Jiri Olsa (21): > uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock > uprobes: Rename arch_uretprobe_trampoline function > uprobes: Make copy_from_page global > uprobes: Add uprobe_write function > uprobes: Add nbytes argument to uprobe_write > uprobes: Add is_register argument to uprobe_write and > uprobe_write_opcode > uprobes: Add do_ref_ctr argument to uprobe_write function > uprobes/x86: Add mapping for optimized uprobe trampolines > uprobes/x86: Add uprobe syscall to speed up uprobe > uprobes/x86: Add support to optimize uprobes > selftests/bpf: Import usdt.h from libbpf/usdt project > 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 > 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 | 525 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- > include/linux/syscalls.h | 2 + > include/linux/uprobes.h | 20 +++- > kernel/events/uprobes.c | 100 > ++++++++++++----- > kernel/fork.c | 1 + > kernel/seccomp.c | 32 ++++-- > kernel/sys_ni.c | 1 + > tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c | 523 > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------ > 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 | 60 +++++++++- > tools/testing/selftests/bpf/test_kmods/bpf_testmod.c | 11 +- > tools/testing/selftests/bpf/usdt.h | 545 > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > tools/testing/selftests/seccomp/seccomp_bpf.c | 107 > ++++++++++++++---- > 17 files changed, 1867 insertions(+), 112 deletions(-) > create mode 100644 tools/testing/selftests/bpf/usdt.h > > > Jiri Olsa (1): > man2: Add uprobe syscall page > > man/man2/uprobe.2 | 1 + > man/man2/uretprobe.2 | 36 ++++++++++++++++++++++++------------ > 2 files changed, 25 insertions(+), 12 deletions(-) > create mode 100644 man/man2/uprobe.2
