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    SubjectRe: [PATCH] Enhance perf to collect KVM guest os statistics from host side

    * Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:

    > On Tue, 2010-03-16 at 15:48 +0800, Zhang, Yanmin wrote:
    > > On Tue, 2010-03-16 at 07:41 +0200, Avi Kivity wrote:
    > > > On 03/16/2010 07:27 AM, Zhang, Yanmin wrote:
    > > > > From: Zhang, Yanmin<yanmin_zhang@linux.intel.com>
    > > > >
    > > > > Based on the discussion in KVM community, I worked out the patch to support
    > > > > perf to collect guest os statistics from host side. This patch is implemented
    > > > > with Ingo, Peter and some other guys' kind help. Yang Sheng pointed out a
    > > > > critical bug and provided good suggestions with other guys. I really appreciate
    > > > > their kind help.
    > > > >
    > > > > The patch adds new subcommand kvm to perf.
    > > > >
    > > > > perf kvm top
    > > > > perf kvm record
    > > > > perf kvm report
    > > > > perf kvm diff
    > > > >
    > > > > The new perf could profile guest os kernel except guest os user space, but it
    > > > > could summarize guest os user space utilization per guest os.
    > > > >
    > > > > Below are some examples.
    > > > > 1) perf kvm top
    > > > > [root@lkp-ne01 norm]# perf kvm --host --guest --guestkallsyms=/home/ymzhang/guest/kallsyms
    > > > > --guestmodules=/home/ymzhang/guest/modules top
    > > > >
    > > > >
    > > >
    > > Thanks for your kind comments.
    > >
    > > > Excellent, support for guest kernel != host kernel is critical (I can't
    > > > remember the last time I ran same kernels).
    > > >
    > > > How would we support multiple guests with different kernels?
    > > With the patch, 'perf kvm report --sort pid" could show
    > > summary statistics for all guest os instances. Then, use
    > > parameter --pid of 'perf kvm record' to collect single problematic instance data.
    > Sorry. I found currently --pid isn't process but a thread (main thread).
    >
    > Ingo,
    >
    > Is it possible to support a new parameter or extend --inherit, so 'perf
    > record' and 'perf top' could collect data on all threads of a process when
    > the process is running?
    >
    > If not, I need add a new ugly parameter which is similar to --pid to filter
    > out process data in userspace.

    Yeah. For maximum utility i'd suggest to extend --pid to include this, and
    introduce --tid for the previous, limited-to-a-single-task functionality.

    Most users would expect --pid to work like a 'late attach' - i.e. to work like
    strace -f or like a gdb attach.

    Ingo


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