Re: [PATCH 19/20] function_graph: Use for_each_set_bit() in __ftrace_return_to_handler()

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Fri, 24 May 2024 22:37:11 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> Instead of iterating through the entire fgraph_array[] and seeing if one
> of the bitmap bits are set to know to call the array's retfunc() function,
> use for_each_set_bit() on the bitmap itself. This will only iterate for
> the number of set bits.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/fgraph.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index 4d503b3e45ad..5e8e13ffcfb6 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -827,11 +827,10 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
>  #endif
>  
>  	bitmap = get_bitmap_bits(current, offset);
> -	for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
> +
> +	for_each_set_bit(i, &bitmap, sizeof(bitmap) * BITS_PER_BYTE) {
>  		struct fgraph_ops *gops = fgraph_array[i];
>  
> -		if (!(bitmap & BIT(i)))
> -			continue;
>  		if (gops == &fgraph_stub)

Ah, nit: maybe this is unlikely()?

Thank you,


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>