From: Yanmin Zhang <firstname.lastname@example.org>
To: Arnaldo Carvalho de Melo <email@example.com>
Cc: Stephane Eranian <firstname.lastname@example.org>,
Avi Kivity <email@example.com>
Subject: Re: [PATCH] perf: fix broken perf inject -b
Date: Tue, 31 Jan 2012 13:58:19 +0800 [thread overview]
Message-ID: <1327989499.14415.230.camel@ymzhang> (raw)
On Mon, 2012-01-30 at 18:36 -0200, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jan 30, 2012 at 09:09:17PM +0100, Stephane Eranian escreveu:
> > On Mon, Jan 30, 2012 at 9:04 PM, Arnaldo Carvalho de Melo
> > <firstname.lastname@example.org> wrote:
> > > Em Mon, Jan 30, 2012 at 08:53:26PM +0100, Stephane Eranian escreveu:
> > >> On Mon, Jan 30, 2012 at 8:00 PM, Arnaldo Carvalho de Melo
> > >> <email@example.com> wrote:
> > >> > > >>> @@ -173,6 +178,7 @@ static int perf_event__inject_buildid(struct perf_tool *tool,
> > >> > > >>> goto repipe;
> > >> > > >>> }
> > >> > > >>> + machine->pid = event->ip.pid;
> > >> >
> > >> > > I noticed that this statement conflicts with perf buildid-list (which
> > >> > > I am also fixing for pipe mode).
> > >> > > I don't quite understand why, though.
> > >> > Have you reached any conclusion about this problem? I haven't looked at
> > >> > it in detail, could you please elaborate more?
> > >> I ended up removing it. But I am not sure this is correct.
> > >> Is the pid used in any way when processing buildids?
> > >
> > > I can't think of any.
> > >
> > > The same DSO could conceivably be present in the virtual machine, the
> > > host, and in the workstation used for perf report. We just use the
> > > build-id in the perf.data file to find the right symtab.
> > Right, so I don't know why it's there...
> This comes from a1645ce1:
> commit a1645ce12adb6c9cc9e19d7695466204e3f017fe
> Author: Zhang, Yanmin <firstname.lastname@example.org>
> Date: Mon Apr 19 13:32:50 2010 +0800
> perf: 'perf kvm' tool for monitoring guest performance from host
> Here is the patch of userspace perf tool.
> Signed-off-by: Zhang Yanmin <email@example.com>
> Signed-off-by: Avi Kivity <firstname.lastname@example.org>
> Zhang, what was the thinking about that pid in the buildid event?
I didn't work on it for a long time because of some special reasons.
I check it quickly and below are some explanation.
machine->pid is to support KVM multiple guest os kernels.
1) The guest os kernels might be different version of kernels from host's;
2) The guest os might be Windows.
At host side, every guest os is a process of host although it's multi-threaded.
machine->pid is to save its pid. The pid of host itself is HOST_KERNEL_ID.
In guest os, there are many processes. host os doesn't know them. So currently or
when I enhanced perf to support KVM, perf filters out guest os user space
detailed event samples while still keeping guest os user space simple counters.
event->ip.pid is equal to machine->pid only when
((event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK) == PERF_RECORD_MISC_GUEST_KERNEL).
In function perf_event__inject_buildid, we shouldn't reset machine->pid to
event->ip.pid. They are equal to each other if it's a guest os event. Isn't it?
If the event is host event, event->ip.pid points to a real process at host
and it shouldn't be equal to machine->pid (HOST_KERNEL_ID).
next prev parent reply other threads:[~2012-01-31 5:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-13 14:47 [PATCH] perf: fix broken perf inject -b Stephane Eranian
2012-01-13 16:53 ` Arnaldo Carvalho de Melo
2012-01-13 16:54 ` Stephane Eranian
2012-01-16 18:53 ` Stephane Eranian
2012-01-30 19:00 ` Arnaldo Carvalho de Melo
2012-01-30 19:53 ` Stephane Eranian
2012-01-30 20:04 ` Arnaldo Carvalho de Melo
2012-01-30 20:09 ` Stephane Eranian
2012-01-30 20:36 ` Arnaldo Carvalho de Melo
2012-01-31 5:58 ` Yanmin Zhang [this message]
2012-02-02 11:22 ` Stephane Eranian
2012-02-03 3:30 ` Yanmin Zhang
2012-01-26 14:16 ` Stephane Eranian
2012-01-26 14:23 ` Arnaldo Carvalho de Melo
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