linux-kernel - Re: [PATCH 20/20] function_graph: Use bitmask to loop on fgraph entry

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Date: Sun, 26 May 2024 20:33:18 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, Mark
 Rutland <mark.rutland@....com>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Alexei Starovoitov
 <alexei.starovoitov@...il.com>, Florent Revest <revest@...omium.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, bpf <bpf@...r.kernel.org>, Sven
 Schnelle <svens@...ux.ibm.com>, Alexei Starovoitov <ast@...nel.org>, Jiri
 Olsa <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>, Alan Maguire <alan.maguire@...cle.com>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner
 <tglx@...utronix.de>, Guo Ren <guoren@...nel.org>
Subject: Re: [PATCH 20/20] function_graph: Use bitmask to loop on fgraph
 entry

On Mon, 27 May 2024 09:09:49 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> > Note, we do not care about races. If a bit is set before the gops is
> > assigned, it only wastes time looking at the element and ignoring it (as
> > it did before this bitmask is added).  
> 
> This is OK because anyway we check gops == &fgraph_stub.
> By the way, shouldn't we also make "if (gops == &fgraph_stub)"
> check unlikely()?

Yeah, I'll add the unlikely() here too.

> 
> This change looks good to me.
> 
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks for the review Masami!

-- Steve