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Date: Mon, 14 Apr 2025 16:57:36 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Junxuan Liao <ljx@cs.wisc.edu>, linux-trace-kernel@vger.kernel.org,
 linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner
 <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
 <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "H. Peter Anvin"
 <hpa@zytor.com>, Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, "Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH] x86/tracing: introduce enter/exit tracepoint pairs for
 page faults
Message-ID: <20250414165736.77415836@gandalf.local.home>
In-Reply-To: <214abd94-7fb3-4515-a1ae-a60abe81af88@intel.com>
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On Mon, 14 Apr 2025 13:42:23 -0700
Dave Hansen <dave.hansen@intel.com> wrote:

> On 4/14/25 13:35, Junxuan Liao wrote:
> > Rename page_fault_{user,kernel} to page_fault_{user,kernel}_enter, and
> > add the exit counterparts. This might be useful for measuring page fault
> > handling latencies.  
> 
> Is there a reason kprobes don't work for this?

Kprobes is not always easy to add, and it does add more overhead.

I use to have measurements by using function graph tracing of all timings
into the kernel, but when the noinstr was added, that broke. I still do
timings but that's by manually adding hacks into the kernel. I haven't done
timings on a vanilla kernel for some time. It would be nice to be able to
do that again.

-- Steve