Re: [PATCH v2] perf report: distinguish between inliners in the same function

From	Milian Wolff <milian.wolff@kdab.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] perf report: distinguish between inliners in the same function
Date	2017-05-18 14:30 +0200
Message-ID	<tIsJ3-2u7-7@gated-at.bofh.it> (permalink)
References	<tDaa6-2vi-17@gated-at.bofh.it> <tHKym-65Z-19@gated-at.bofh.it> <tI0ts-7Un-3@gated-at.bofh.it>
Organization	KDAB (Deutschland) GmbH&Co KG, a KDAB Group company

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On Mittwoch, 17. Mai 2017 08:13:16 CEST Namhyung Kim wrote:
> On Tue, May 16, 2017 at 03:18:13PM +0200, Milian Wolff wrote:
> > On Dienstag, 16. Mai 2017 02:53:32 CEST Namhyung Kim wrote:
> > > On Mon, May 15, 2017 at 12:01:54PM +0200, Milian Wolff wrote:
> > > > On Monday, May 15, 2017 3:21:58 AM CEST Namhyung Kim wrote:
> > > > > Hi Milian,
> > > > > 
> > > > > On Sun, May 14, 2017 at 08:10:50PM +0200, Milian Wolff wrote:
> > > > > > On Freitag, 12. Mai 2017 15:01:29 CEST Namhyung Kim wrote:
> > > > > I think you'd be better adding (fake) dso and sym to keep the inline
> > > > > information.  The fake dso can be paired with the original dso and
> > > > > maintain a tree of (inlined) symbols.  You may need a fake map to
> > > > > point the fake dso then.  It seems a bit compilcated but that way
> > > > > the
> > > > > code will be more consistent and easier to handle (e.g. for caching
> > > > > and/or deletion) IMHO.
> > > > 
> > > > Can you expand on this please? How would that solve the problem of
> > > > finding
> > > > a function name or srcline for a given inline frame?
> > > > 
> > > > I.e.: the function name is, currently, part of the sym. So the fake
> > > > dso/map
> > > > would contain an internal, fake, string table which fake symbols could
> > > > leverage for the function name?
> > > > 
> > > > Sounds like doable, but also sounds like *a lot* of work. And I don't
> > > > see
> > > > how that would solve the srcline situation: That one is queried
> > > > on-demand
> > > > based on the IP of a frame. I would say that inline frames should keep
> > > > the IP of the first non-inlined frame. But that would make it
> > > > impossible
> > > > to find the srcline for the N'th inlined frame... Am I missing
> > > > something?
> > > 
> > > I agree that srcline info can be kept in callchain cursor nodes, but I
> > > still think function name should be in (fake) symbols.  Sharing a
> > > symbol for all inlined frames would not work for the children mode
> > > IMHO.
> > 
> > I'm running into a bit of trouble here. I hoped to be able to store the
> > inlined symbol in the DSO to reuse it for other inlined entries that use
> > the same function. I also hope that this will then take care of the
> > deletion of the fake symbols, once the dso is freed.
> 
> I don't want to store inlined functions to an original DSO as it would
> confuse symbol lookups in the DSO.  As you said those inlined
> functions will have same address so multiple symbols exist for an
> address.
> 
> I thought they can be kept in a fake DSO which should be linked to the
> original DSO, but it doesn't need to be a DSO.  Instead a DSO can have
> a tree that maintains lists of (inlined) symbols and srclines sorted
> by address.

Thank you, this is what I'll be doing now.

Cheers

-- 
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

Thread

Re: [PATCH v2] perf report: distinguish between inliners in the same function Milian Wolff <milian.wolff@kdab.com> - 2017-05-12 12:40 +0200
  Re: [PATCH v2] perf report: distinguish between inliners in the same  function Namhyung Kim <namhyung@kernel.org> - 2017-05-12 15:10 +0200
    Re: [PATCH v2] perf report: distinguish between inliners in the same function Milian Wolff <milian.wolff@kdab.com> - 2017-05-14 20:20 +0200
      Re: [PATCH v2] perf report: distinguish between inliners in the same  function Namhyung Kim <namhyung@kernel.org> - 2017-05-15 03:30 +0200
        Re: [PATCH v2] perf report: distinguish between inliners in the same function Milian Wolff <milian.wolff@kdab.com> - 2017-05-15 12:10 +0200
          Re: [PATCH v2] perf report: distinguish between inliners in the same  function Namhyung Kim <namhyung@kernel.org> - 2017-05-16 03:00 +0200
            Re: [PATCH v2] perf report: distinguish between inliners in the same function Milian Wolff <milian.wolff@kdab.com> - 2017-05-16 15:20 +0200
              Re: [PATCH v2] perf report: distinguish between inliners in the same  function Namhyung Kim <namhyung@kernel.org> - 2017-05-17 08:20 +0200
                Re: [PATCH v2] perf report: distinguish between inliners in the same function Milian Wolff <milian.wolff@kdab.com> - 2017-05-18 14:30 +0200
  Re: [PATCH v2] perf report: distinguish between inliners in the same function Andi Kleen <andi@firstfloor.org> - 2017-05-12 17:00 +0200
    Re: [PATCH v2] perf report: distinguish between inliners in the same  function Namhyung Kim <namhyung@kernel.org> - 2017-05-15 02:50 +0200

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