linux-kernel - Re: [PATCH v12 08/11] perf tools: Minimal CALLCHAIN

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Message-ID: <51903e66-56bc-42a4-b80c-9c3223e2a48a@linux.ibm.com>
Date: Wed, 2 Jul 2025 14:23:24 +0200
From: Jens Remus <jremus@...ux.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org,
        x86@...nel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrii Nakryiko <andrii@...nel.org>,
        Indu Bhagat <indu.bhagat@...cle.com>,
        "Jose E. Marchesi" <jemarch@....org>,
        Beau Belgrave <beaub@...ux.microsoft.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, Florian Weimer <fweimer@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v12 08/11] perf tools: Minimal CALLCHAIN_DEFERRED support

Hello Steve!

On 01.07.2025 20:04, Steven Rostedt wrote:
> From: Namhyung Kim <namhyung@...nel.org>
> 
> Add a new event type for deferred callchains and a new callback for the
> struct perf_tool.  For now it doesn't actually handle the deferred
> callchains but it just marks the sample if it has the PERF_CONTEXT_
> USER_DEFFERED in the callchain array.

> diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h

> @@ -151,6 +151,12 @@ struct perf_record_switch {
>  	__u32			 next_prev_tid;
>  };
>  
> +struct perf_record_callchain_deferred {
> +	struct perf_event_header header;

At minimum the timestamp field added to perf with "[PATCH v12 07/11]
perf: Support deferred user callchains for per CPU events" needs to be
added here as well:

	__u64			 timestamp;

Otherwise this and any subsequent enhancements of the perf tools do no
longer work at all.  But probably the timestamp field also needs to be
used for some purpose?

> +	__u64			 nr;
> +	__u64			 ips[];
> +};
> +

Thanks and regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@...ibm.com

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