Re: Emulate Rpi with QEMU fails

[Paul Zimmerman <pauldzim@gmail.com>]

Running 'top -H' (to show individual threads) I see qemu is using 6 to 7
threads while running, and each thread is taking from 15% to 70% or so
of cpu time. So probably qemu is not able to spread the work among the
threads evenly enough to use all the cpu time available.

Might be an interesting area of investigation for someone motivated
enough :)

- Paul

On Thu, Oct 8, 2020 at 2:07 PM Paul Zimmerman <pauldzim@gmail.com> wrote:
>
> Hi Thomas,
>
> What does 'top' say while the emulation is running? I have an 8 cpu-thread
> system, yet 'top' never shows more than about 300% cpu. I would have
> thought it would get closer to 800% cpu. And running qemu as root with
> nice -20 doesn't seem to make much difference.
>
> - Paul
>
> On Thu, Oct 8, 2020 at 12:00 AM Thomas <74cmonty@gmail.com> wrote:
> >
> > Interesting enough is: my top figure reported by perf is like yours:
> >
> > Samples: 6M of event 'cycles:u', Event count (approx.): 1936571734942
> > Overhead  Command          Shared Object                  Symbol
> >    7,95%  qemu-system-arm  qemu-system-arm                [.]
> > helper_lookup_tb_ptr
> > ◆
> >    4,16%  qemu-system-arm  qemu-system-arm                [.]
> > cpu_get_tb_cpu_state
> > ▒
> >    2,52%  qemu-system-arm  libpthread-2.32.so             [.]
> > __pthread_mutex_lock
> > ▒
> >    2,06%  qemu-system-arm  qemu-system-arm                [.]
> > qht_lookup_custom
> > ▒
> >    1,66%  qemu-system-arm  qemu-system-arm                [.]
> > tlb_set_page_with_attrs
> > ▒
> >    1,61%  qemu-system-arm  libpthread-2.32.so             [.]
> > __pthread_mutex_unlock_usercnt
> > ▒
> >    1,59%  qemu-system-arm  qemu-system-arm                [.]
> > get_phys_addr
> > ▒
> >    1,27%  qemu-system-arm  qemu-system-arm                [.]
> > cpu_exec
> > ▒
> >    1,23%  qemu-system-arm  qemu-system-arm                [.]
> > object_class_dynamic_cast_assert
> > ▒
> >    0,98%  qemu-system-arm  libc-2.32.so                   [.]
> > _int_malloc
> > ▒
> >    0,95%  qemu-system-arm  qemu-system-arm                [.]
> > object_dynamic_cast_assert
> > ▒
> >    0,95%  qemu-system-arm  qemu-system-arm                [.]
> > tb_htable_lookup
> > ▒
> >    0,92%  qemu-system-arm  qemu-system-arm                [.]
> > tcg_gen_code
> > ▒
> >    0,91%  qemu-system-arm  qemu-system-arm                [.]
> > qemu_mutex_lock_impl
> > ▒
> >    0,75%  qemu-system-arm  qemu-system-arm                [.]
> > get_page_addr_code_hostp
> > ▒
> >    0,73%  qemu-system-arm  qemu-system-arm                [.]
> > tcg_optimize
> > ▒
> >    0,71%  qemu-system-arm  qemu-system-arm                [.]
> > qemu_mutex_unlock_impl
> > ▒
> >    0,69%  qemu-system-arm  libc-2.32.so                   [.]
> > _int_free
> > ▒
> >    0,64%  qemu-system-arm  qemu-system-arm                [.]
> > tb_flush_jmp_cache
> > ▒
> >    0,63%  qemu-system-arm  qemu-system-arm                [.]
> > address_space_ldl_le
> > ▒
> >    0,62%  qemu-system-arm  libpthread-2.32.so             [.]
> > __lll_lock_wait
> > ▒
> >    0,58%  qemu-system-arm  libpthread-2.32.so             [.]
> > pthread_cond_wait@@GLIBC_2.3.2
> > ▒
> >    0,52%  qemu-system-arm  qemu-system-arm                [.]
> > cpu_reset_interrupt
> > ▒
> >    0,52%  qemu-system-arm  libc-2.32.so                   [.]
> > cfree@GLIBC_2.2.5
> > ▒
> >    0,52%  qemu-system-arm  qemu-system-arm                [.]
> > qemu_set_irq
> > ▒
> >
> > However the absolute time is 3-4 minutes.
> > And I don't know where I should start optimization now.
> >
> >
> >
> > Am 07.10.20 um 14:02 schrieb Alex Bennée:
> > > Thomas Schneider <74cmonty@gmail.com> writes:
> > >
> > >> Are you referring to this tool?
> > >> https://github.com/stefano-garzarella/qemu-boot-time
> > >> <https://github.com/stefano-garzarella/qemu-boot-time>
> > > No - just plain perf:
> > >
> > >   perf record $QEMU $ARGS
> > >
> > > Then a "perf report" which will show you the hotspots, for example:
> > >
> > >    8.92%  qemu-system-aar  qemu-system-aarch64      [.] helper_lookup_tb_ptr
> > >    4.76%  qemu-system-aar  qemu-system-aarch64      [.] liveness_pass_1
> > >    3.69%  qemu-system-aar  qemu-system-aarch64      [.] tcg_gen_code
> > >    2.95%  qemu-system-aar  qemu-system-aarch64      [.] qht_lookup_custom
> > >    2.93%  qemu-system-aar  qemu-system-aarch64      [.] tcg_optimize
> > >    1.28%  qemu-system-aar  qemu-system-aarch64      [.] tcg_out_opc.isra.15
> > >    1.09%  qemu-system-aar  qemu-system-aarch64      [.] get_phys_addr_lpae
> > >    1.09%  qemu-system-aar  [kernel.kallsyms]        [k] isolate_freepages_block
> > >    1.05%  qemu-system-aar  qemu-system-aarch64      [.] cpu_get_tb_cpu_state
> > >    0.98%  qemu-system-aar  [kernel.kallsyms]        [k] do_syscall_64
> > >    0.94%  qemu-system-aar  qemu-system-aarch64      [.] tb_lookup_cmp
> > >    0.78%  qemu-system-aar  qemu-system-aarch64      [.] init_ts_info
> > >    0.73%  qemu-system-aar  qemu-system-aarch64      [.] tb_htable_lookup
> > >    0.73%  qemu-system-aar  qemu-system-aarch64      [.] tb_gen_code
> > >    0.73%  qemu-system-aar  qemu-system-aarch64      [.] tlb_set_page_with_attrs
> > >
> > >>
> > >> Am 07.10.2020 um 13:00 schrieb Alex Bennée:
> > >>> perf to record your boot
> > >
> >