linux-kernel - Re: [PATCH v5 1/2] function_graph: Support recording and printing the return value of function

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Date:   Tue, 21 Mar 2023 15:09:40 +0100
From:   Florian Kauer <florian.kauer@...utronix.de>
To:     Donglin Peng <pengdonglin@...gfor.com.cn>, mhiramat@...nel.org,
        rostedt@...dmis.org, linux@...linux.org.uk, mark.rutland@....com,
        will@...nel.org, catalin.marinas@....com, palmer@...belt.com,
        paul.walmsley@...ive.com, tglx@...utronix.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, mingo@...hat.com,
        xiehuan09@...il.com, dinghui@...gfor.com.cn,
        huangcun@...gfor.com.cn, dolinux.peng@...il.com
Cc:     linux-trace-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/2] function_graph: Support recording and printing the
 return value of function

On 20.03.23 14:16, Donglin Peng wrote:
> When using the function_graph tracer to analyze system call failures,
> it can be time-consuming to analyze the trace logs and locate the kernel
> function that first returns an error. This change aims to simplify the
> process by recording the function return value to the 'retval' member of
> 'ftrace_graph_ent' and printing it when outputing the trace log.

I just came across your patch by pure luck and it helped me a lot
to trace down a problem I had, thanks!

So you can have my
Tested-by: Florian Kauer <florian.kauer@...utronix.de>
 
> New trace options are introduced: funcgraph-retval and graph_retval_hex.

I would personally prefer to have the second option scoped better, so for example
"funcgraph-retval-hex".

Greetings,
Florian