Messages in this thread | | | Date | Wed, 23 Feb 2022 16:00:27 +0800 | Subject | Re: [External] Re: [PATCH] arm64/ftrace: Make function graph use ftrace directly | From | Chengming Zhou <> |
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On 2022/2/22 11:52 下午, Steven Rostedt wrote: > On Tue, 22 Feb 2022 21:00:49 +0800 > Chengming Zhou <zhouchengming@bytedance.com> wrote: > >> As we do in commit 0c0593b45c9b ("x86/ftrace: Make function graph >> use ftrace directly"), we don't need special hook for graph tracer, >> but instead we use graph_ops:func function to install return_hooker. >> >> Since commit 3b23e4991fb6 ("arm64: implement ftrace with regs") add >> implementation for FTRACE_WITH_REGS on arm64, we can easily adopt >> the same optimization on arm64. > > Note. Ideally we want it to hook with DYNAMIC_FTARCE_WITH_ARGS, and not > FTRACE_WITH_REGS. If arm64 is like x86_64, saving all regs at every > function call has a bit more overhead than saving the minimum. The > DYNAMIC_FTRACE_WITH_ARGS, means that the minimum is still saved, but now > exposes the arguments and the stack pointer, which function_graph_tracer > needs.
Yes, it would be better to implement DYNAMIC_FTRACE_WITH_ARGS on arm64 too, and this patch just use DYNAMIC_FTRACE_WITH_REGS to install return_hooker for graph tracer, so it's a code cleanup, no performance optimization.
Thanks.
> > -- Steve > > >> >> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> >> ---
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