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From: Steven Rostedt <rostedt@goodmis.org>
To: Yordan Karadzhov <y.karadz@gmail.com>
Cc: Linux Trace Devel <linux-trace-devel@vger.kernel.org>
Subject: Re: [PATCH] kernel-shark: Add check for return of ksmodel_get_cpu_front()
Date: Tue, 11 May 2021 09:40:45 -0400	[thread overview]
Message-ID: <20210511094045.1673b76a@gandalf.local.home> (raw)
In-Reply-To: <2bc740d1-e093-17d1-a9ba-b4319e0ebbfa@gmail.com>

On Tue, 11 May 2021 16:25:35 +0300
Yordan Karadzhov <y.karadz@gmail.com> wrote:

> > You can reproduce this with:
> > 
> >     http://rostedt.org/private/trace-no-map.tar.bz2
> > 
> > diff --git a/src/KsPlotTools.cpp b/src/KsPlotTools.cpp
> > index 225dc34..abef5f8 100644
> > --- a/src/KsPlotTools.cpp
> > +++ b/src/KsPlotTools.cpp
> > @@ -1280,7 +1280,7 @@ void Graph::fillTaskGraph(int sd, int pid)
> >   						 false,
> >   						 _collectionPtr,
> >   						 &index);  
> 
> I wonder why this fails? Is it because "pid" is negative? The fix below 
> is appropriate, however we should detect negative PIDs and abort 
> plotting much earlier.

I believe the issue is that we failed to map which host task goes with
which guest vCPUU, and just randomly picked one (or none).

I fixed trace-cmd to get the mappings when qemu is not found, and
KernelShark works fine on that case. This bug only appears when it can't
find the host thread that corresponds to the guest vCPU.

-- Steve

  reply	other threads:[~2021-05-11 13:40 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-07 13:38 [PATCH] kernel-shark: Add check for return of ksmodel_get_cpu_front() Steven Rostedt
2021-05-11 13:25 ` Yordan Karadzhov
2021-05-11 13:40   ` Steven Rostedt [this message]
2021-05-11 13:51     ` Yordan Karadzhov
2021-05-14 11:50 ` Yordan Karadzhov

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