linux-kernel - Re: [PATCH v3 08/10] mm: frontswap: add tracing support

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Message-ID: <1339411150.4999.43.camel@lappy>
Date:	Mon, 11 Jun 2012 12:39:10 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	Minchan Kim <minchan@...nel.org>, dan.magenheimer@...cle.com,
	konrad.wilk@...cle.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH v3 08/10] mm: frontswap: add tracing support

On Mon, 2012-06-11 at 11:33 +0300, Pekka Enberg wrote:
> On 06/10/2012 07:51 PM, Sasha Levin wrote:
> >> Add tracepoints to frontswap API.
> >>
> >> Signed-off-by: Sasha Levin <levinsasha928@...il.com>
> 
> On Mon, Jun 11, 2012 at 9:12 AM, Minchan Kim <minchan@...nel.org> wrote:
> > Normally, adding new tracepoint isn't easy without special reason.
> > I'm not sure all of frontswap function tracing would be valuable.
> > Shsha, Why do you want to add tracing?
> > What's scenario you want to use tracing?

I added tracing when working on code to integrate KVM with
frontswap/cleancache and needed to see that the flow of code between
host side kvm and zcache and guest side cleancache, frontswap and kvm is
correct.

> Yup, the added tracepoints look more like function tracing. Shouldn't
> you use something like kprobes or ftrace/perf for this?

I'm not sure really, there are quite a few options provided by the
kernel...

I used tracepoints because I was working on code that integrates with
KVM, and saw that KVM was working with tracepoints in a very similar way
to what I needed, so I assumed tracepoints is the right choice for me.

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