linux-kernel - Re: [PATCH v6 17/22] arm64: mm: Add page fault trace points

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Message-ID: <20250519120837.794f6738@batman.local.home>
Date: Mon, 19 May 2025 12:08:37 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Will Deacon <will@...nel.org>
Cc: Nam Cao <namcao@...utronix.de>, Gabriele Monaco <gmonaco@...hat.com>,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
 john.ogness@...utronix.de, Catalin Marinas <catalin.marinas@....com>,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 17/22] arm64: mm: Add page fault trace points

On Mon, 19 May 2025 16:12:39 +0100
Will Deacon <will@...nel.org> wrote:

> > Perf events work for perf only. My question is why isn't this a tracepoint
> > that perf could hook into?  
> 
> Well, the perf event came first in this case, so we're stuck with it :/

I wonder what effort it will take to convert perf events to tracepoints ;-)

Note, I'm talking about tracepoints and not trace events, where the
latter is exposed to tracefs and the former is not.

> 
> I was hoping we could settle for a generic helper that could emit both
> the trace event and the perf event (so that the ordering of the two is
> portable across architectures) but, judging by Nam's reply, the trace
> event is needed before kprobes gets a look in.

Perhaps we could add a helper function that does both (perf and
tracepoint) and hide the implementation from the code that calls it?

But I'm currently still on PTO so I haven't looked at the details yet.

-- Steve