linux-kernel - Re: [BUG] msr-trace.h:42 suspicious rcu_dereference

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Message-ID: <20161123210618.5103f25d@gandalf.local.home>
Date:   Wed, 23 Nov 2016 21:06:18 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Jan Stancek <jstancek@...hat.com>
Subject: Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

On Mon, 21 Nov 2016 10:37:00 -0800
Andi Kleen <andi@...stfloor.org> wrote:

> > It tries to be optimized. I "unoptimized" it a while back to pull out
> > all the inlines that were done in the tracepoint itself. That is, the
> > trace_<tracepoint>() function is inlined in the code itself. By
> > breaking that up a bit, I was able to save a bunch of text because the
> > tracepoints were bloating the kernel tremendously.  
> 
> Just adding a few inlines won't fix the gigantic bloat that is currently
> there. See the PT trace I posted earlier (it was even truncated, it's
> actually worse). Just a single enabled trace point took about a us.
> 
> POPF can cause some serializion but it won't be more than a few tens
> of cycles, which would be a few percent at best.
> 
> Here is it again untruncated:
> 
> http://halobates.de/tracepoint-trace
> 

I took a look at this and forced some more functions to be inlined. I
did a little tweaking here and there. Could you pull my tree and see if
things are better?  I don't currently have the hardware to run this
myself.

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git

  branch: ftrace/core


Thanks!

-- Steve