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SubjectRe: [PATCH 04/11] perf kvm: fix bug resolving guest kernel syms - v2
On Fri, Jul 20, 2012 at 05:25:49PM -0600, David Ahern wrote:
> Guest kernel symbols are not resolved despite passing the information
> needed to resolve them. e.g.,
>
> perf kvm --guest --guestmount=/tmp/guest-mount record -a -- sleep 1
> perf kvm --guest --guestmount=/tmp/guest-mount report --stdio
>
> 36.55% [guest/11399] [unknown] [g] 0xffffffff81600bc8
> 33.19% [guest/10474] [unknown] [g] 0x00000000c0116e00
> 30.26% [guest/11094] [unknown] [g] 0xffffffff8100a288
> 43.69% [guest/10474] [unknown] [g] 0x00000000c0103d90
> 37.38% [guest/11399] [unknown] [g] 0xffffffff81600bc8
> 12.24% [guest/11094] [unknown] [g] 0xffffffff810aa91d
> 6.69% [guest/11094] [unknown] [u] 0x00007fa784d721c3
>
> which is just pathetic.
>
> After a maddening 2 days sifting through perf minutia I found it --
> id_hdr_size is not initialized for guest machines. This shows up on the
> report side as random garbage for the cpu and timestamp, e.g.,
>
> 29816 7310572949125804849 0x1ac0 [0x50]: PERF_RECORD_MMAP ...
>
> That messes up the sample sorting such that synthesized guest maps are
> processed last.
>
> With this patch you get a much more helpful report:
>
> 12.11% [guest/11399] [guest.kernel.kallsyms.11399] [g] irqtime_account_process_tick
> 10.58% [guest/11399] [guest.kernel.kallsyms.11399] [g] run_timer_softirq
> 6.95% [guest/11094] [guest.kernel.kallsyms.11094] [g] printk_needs_cpu
> 6.50% [guest/11094] [guest.kernel.kallsyms.11094] [g] do_timer
> 6.45% [guest/11399] [guest.kernel.kallsyms.11399] [g] idle_balance
> 4.90% [guest/11094] [guest.kernel.kallsyms.11094] [g] native_read_tsc
> ...
>
> v2:
> - changed rbtree walk to use rb_first per Namhyung's suggestion
>
> Signed-off-by: David Ahern <dsahern@gmail.com>
> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Jiri Olsa <jolsa@redhat.com>

Tested-by: Jiri Olsa <jolsa@redhat.com>


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