Re: [Qemu-devel] Hack integrating SeaBios / LinuxBoot option rom with QEMU trace backends

[Avi Kivity <avi@redhat.com>]

On 10/11/2011 11:18 AM, Daniel P. Berrange wrote:
> >
> >  The rep/ins implementation is still slow, optimizing it can help.
> >
> >  What does 'perf top' say when running this workload?
>
> To ensure it only recorded the LinuxBoot code, I created a 100 MB
> kernel image which takes approx 30 seconds to copy. Here is the
> perf output for approx 15 seconds of that copy:
>
>               1906.00 15.0% read_hpet                       [kernel]

Recent kernels are very clock intensive...

>               1029.00  8.1% x86_emulate_insn                [kvm]
>                863.00  6.8% test_cc                         [kvm]

test_cc() is wierd - not called on this path at all.

>                661.00  5.2% emulator_get_segment            [kvm]
>                631.00  5.0% kvm_mmu_pte_write               [kvm]
>                535.00  4.2% __linearize                     [kvm]
>                431.00  3.4% do_raw_spin_lock                [kernel]
>                356.00  2.8% vmx_get_segment                 [kvm_intel]
>                330.00  2.6% vmx_segment_cache_test_set      [kvm_intel]
>                308.00  2.4% segmented_write                 [kvm]
>                291.00  2.3% vread_hpet                      [kernel].vsyscall_fn
>                251.00  2.0% vmx_get_cpl                     [kvm_intel]
>                230.00  1.8% trace_kvm_mmu_audit             [kvm]
>                207.00  1.6% kvm_write_guest                 [kvm]
>                199.00  1.6% emulator_write_emulated         [kvm]
>                187.00  1.5% emulator_write_emulated_onepage [kvm]
>                185.00  1.5% kvm_write_guest_page            [kvm]
>                177.00  1.4% vmx_get_segment_base            [kvm_intel]
>                158.00  1.2% fw_cfg_io_readb                 qemu-system-x86_64

This is where something gets done.

>                148.00  1.2% register_address_increment      [kvm]
>                142.00  1.1% emulator_write_phys             [kvm]

And here too.  So 97.7% overhead, which could be reduced by a factor of 
4096 if the code is made more rep-aware.



-- 
error compiling committee.c: too many arguments to function