linux-kernel - Re: [PATCH] perf script: Fix LBR skid dump problems in brstackinsn

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Message-ID: <1690253.Gbn1XyeY7h@agathebauer>
Date:   Tue, 11 Dec 2018 21:47:41 +0100
From:   Milian Wolff <milian.wolff@...b.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-kernel@...r.kernel.org, jolsa@...nel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] perf script: Fix LBR skid dump problems in brstackinsn

On Donnerstag, 6. Dezember 2018 23:52:07 CET Andi Kleen wrote:
> On Thu, Dec 06, 2018 at 06:29:20PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Dec 06, 2018 at 12:51:48PM -0800, Andi Kleen escreveu:
> > > On Thu, Dec 06, 2018 at 02:01:40PM -0300, Arnaldo Carvalho de Melo 
wrote:
> > > > Em Mon, Nov 19, 2018 at 09:06:17PM -0800, Andi Kleen escreveu:
> > > > > From: Andi Kleen <ak@...ux.intel.com>
> > > > > 
> > > > > This is a fix for another instance of the skid problem Milian
> > > > > recently found [1]
> > 
> > I think you forgot to add the reference, i.e. what is the url or
> > message-id that this [1] refers to?
> 
> Hmm, I thought I saw some patches from Milian for this earlier,
> but now I can't find them. Perhaps I misremember. Milian
> can point to them if they exist and are not just a figment
> of my imagination :-)

I only have very early POC patches, cf.: https://lkml.org/lkml/2018/11/14/608

I've now also pushed that on my WIP branch: https://github.com/milianw/linux/
tree/pebs-callchain-breakage

I haven't had the time since to work on this. The patches as-is are not 
upstreamable. There are some open questions on my side (see mail referenced 
above).

> These were the changes to report the stack frame RIP/RSP in the PEBS
> handler and use it for unwinding in perf.

Yes, I was looking at something different. I've no experience with brstackinsn 
usage in perf, so I can't really add my tested-by.

Cheers

-- 
Milian Wolff | milian.wolff@...b.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
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