uprobe: uretprobe speed up #6587
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Adding uretprobe syscall instead of trap to speed up return probe.
At the moment the uretprobe setup/path is:
- install entry uprobe
- when the uprobe is hit overwrite probed function's return address on stack
with address of the trampoline that contains breakpoint instruction
- the breakpoint trap code handles the uretprobe consumers execution and
jumps back to original return address
This patch changes the above trampoline's breakpoint instruction to new
ureprobe syscall call. This syscall does exactly the same job as the trap
with some extra work:
- syscall trampoline must save original value for rax/r11/rcx registers
on stack - rax is set to syscall number and r11/rcx are changed and
used by syscall instruction
- the syscall code reads the original values of those registers and restore
those values in task's pt_regs area
Even with the extra registers handling code the having uretprobes handled
by syscalls shows speed improvement.
On Intel (11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz)
current:
base : 15.173 ± 0.052M/s
uprobe-nop : 2.797 ± 0.090M/s
uprobe-push : 2.580 ± 0.007M/s
uprobe-ret : 1.001 ± 0.003M/s
uretprobe-nop : 1.373 ± 0.002M/s
uretprobe-push : 1.346 ± 0.002M/s
uretprobe-ret : 0.747 ± 0.001M/s
with the fix:
base : 15.704 ± 0.076M/s
uprobe-nop : 2.841 ± 0.008M/s
uprobe-push : 2.666 ± 0.029M/s
uprobe-ret : 1.037 ± 0.008M/s
uretprobe-nop : 1.718 ± 0.010M/s < ~25% speed up
uretprobe-push : 1.658 ± 0.008M/s < ~23% speed up
uretprobe-ret : 0.853 ± 0.004M/s < ~14% speed up
On Amd (AMD Ryzen 7 5700U)
current:
base : 5.702 ± 0.003M/s
uprobe-nop : 1.505 ± 0.011M/s
uprobe-push : 1.388 ± 0.008M/s
uprobe-ret : 0.825 ± 0.001M/s
uretprobe-nop : 0.782 ± 0.001M/s
uretprobe-push : 0.750 ± 0.001M/s
uretprobe-ret : 0.544 ± 0.001M/s
with the fix:
base : 5.669 ± 0.004M/s
uprobe-nop : 1.539 ± 0.001M/s
uprobe-push : 1.385 ± 0.003M/s
uprobe-ret : 0.819 ± 0.001M/s
uretprobe-nop : 0.889 ± 0.001M/s < ~13% speed up
uretprobe-push : 0.846 ± 0.001M/s < ~12% speed up
uretprobe-ret : 0.594 ± 0.000M/s < ~9% speed up
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Add uretprobe syscall test and compare register values before and after the uretprobe is hit. Also compare the register values seen from attached bpf program. Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Some distros seem to enable the -fcf-protection=branch by default, which breaks our setup on first instruction of uprobe trigger functions and place there endbr64 instruction. Marking them with nocf_check attribute to skip that. Adding -Wno-attributes for bench objects, becase nocf_check can be used only when -fcf-protection=branch is enabled, otherwise we get a warning and break compilation. Signed-off-by: Jiri Olsa <jolsa@kernel.org>
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Upstream branch: 4c8644f |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=836016 expired. Closing PR. |
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Pull request for series with
subject: uprobe: uretprobe speed up
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=836016