Messages in this thread | | | Subject | Re: [PATCH] perf: fix broken perf inject -b | From | Yanmin Zhang <> | Date | Tue, 31 Jan 2012 13:58:19 +0800 |
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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 > > <acme@redhat.com> 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 > > >> <acme@redhat.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 <yanmin_zhang@linux.intel.com> > 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 <yanmin_zhang@linux.intel.com> > Signed-off-by: Avi Kivity <avi@redhat.com> > > > > 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).
Yanmin
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