From b56c68f705cad0cff61fbe132c66ced2c737c65c Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 3 Jan 2023 12:49:12 +0000 Subject: ftrace: Add sample with custom ops When reworking core ftrace code or architectural ftrace code, it's often necessary to test/analyse/benchmark a number of ftrace_ops configurations. This patch adds a module which can be used to explore some of those configurations. I'm using this to benchmark various options for changing the way trampolines and handling of ftrace_ops work on arm64, and ensuring other architectures aren't adversely affected. For example, in a QEMU+KVM VM running on a 2GHz Xeon E5-2660 workstation, loading the module in various configurations produces: | # insmod ftrace-ops.ko | ftrace_ops: registering: | relevant ops: 1 | tracee: tracee_relevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | irrelevant ops: 0 | tracee: tracee_irrelevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | saving registers: NO | assist recursion: NO | assist RCU: NO | ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1681558ns (16ns / call) | # insmod ftrace-ops.ko nr_ops_irrelevant=5 | ftrace_ops: registering: | relevant ops: 1 | tracee: tracee_relevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | irrelevant ops: 5 | tracee: tracee_irrelevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | saving registers: NO | assist recursion: NO | assist RCU: NO | ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1693042ns (16ns / call) | # insmod ftrace-ops.ko nr_ops_relevant=2 | ftrace_ops: registering: | relevant ops: 2 | tracee: tracee_relevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | irrelevant ops: 0 | tracee: tracee_irrelevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | saving registers: NO | assist recursion: NO | assist RCU: NO | ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 11965582ns (119ns / call) | # insmod ftrace-ops.ko save_regs=true | ftrace_ops: registering: | relevant ops: 1 | tracee: tracee_relevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | irrelevant ops: 0 | tracee: tracee_irrelevant [ftrace_ops] | tracer: ops_func_nop [ftrace_ops] | saving registers: YES | assist recursion: NO | assist RCU: NO | ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 4459624ns (44ns / call) Link: https://lkml.kernel.org/r/20230103124912.2948963-4-mark.rutland@arm.com Cc: Florent Revest Acked-by: Masami Hiramatsu (Google) Signed-off-by: Mark Rutland Signed-off-by: Steven Rostedt (Google) --- samples/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'samples/Kconfig') diff --git a/samples/Kconfig b/samples/Kconfig index 0d81c00289ee..daf14c35f071 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -46,6 +46,13 @@ config SAMPLE_FTRACE_DIRECT_MULTI that hooks to wake_up_process and schedule, and prints the function addresses. +config SAMPLE_FTRACE_OPS + tristate "Build custom ftrace ops example" + depends on FUNCTION_TRACER + help + This builds an ftrace ops example that hooks two functions and + measures the time taken to invoke one function a number of times. + config SAMPLE_TRACE_ARRAY tristate "Build sample module for kernel access to Ftrace instancess" depends on EVENT_TRACING && m -- cgit