qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] Profiling sparc64 emulation


From: Aurelien Jarno
Subject: Re: [Qemu-devel] Profiling sparc64 emulation
Date: Thu, 9 May 2013 20:30:29 +0200
User-agent: Mutt/1.5.20 (2009-06-14)

On Wed, May 08, 2013 at 11:02:24PM +0200, Artyom Tarasenko wrote:
> On Wed, May 8, 2013 at 12:57 AM, Aurelien Jarno <address@hidden> wrote:
> > On Tue, May 07, 2013 at 11:29:20PM +0200, Artyom Tarasenko wrote:
> >> On Tue, May 7, 2013 at 1:38 PM, Torbjorn Granlund <address@hidden> wrote:
> >> > The 2nd table of http://gmplib.org/devel/testsystems.html shows all
> >> > emulated systems I am using, most of which are qemu-based.
> >>
> >> Do I read it correct that qemu-system-ppc64 with the slowdown factor
> >> of 33 is ~3 times faster than qemu-system-sparc64 with the slowdown
> >> factor of 96 ?
> >> Do they both use Debian Wheezy guest? You have a remark that ppc64 has
> >> problems with its clock. Was it taken into account when the slowdown
> >> factors were calculated?
> >>
> >
> > Clock or not, it should be noted that qemu-system-sparc64 is undoubtedly
> > slower (at least 5 to 10 times) than qemu-system-{arm,ppc,mips,...} on
> > some type of load like perl scripts.
> 
> That's interesting. Actually it should be possible to lauch perl under user
> mode qemu-sparc32plus. Is it possible to launch perl under user mode
> qemu-ppc{32,64} too?
> 
> That would allow to understand whether the bad performance has to do
> with TCG or the rest of the system emulation.

I haven't done that yet, but I have run perf top while running perl
script (lintian), on both qemu-system-sparc64 and qemu-system-ppc64. The
results are quite different:

qemu-system-ppc64
-----------------
 49,73%  perf-10672.map           [.] 0x7f7853ab4e0f
 13,23%  qemu-system-ppc64        [.] cpu_ppc_exec
 13,16%  libglib-2.0.so.0.3200.4  [.] g_hash_table_lookup
  8,18%  libglib-2.0.so.0.3200.4  [.] g_str_hash
  2,47%  qemu-system-ppc64        [.] object_class_dynamic_cast
  1,97%  qemu-system-ppc64        [.] type_is_ancestor
  1,05%  libglib-2.0.so.0.3200.4  [.] g_str_equal
  0,91%  qemu-system-ppc64        [.] ppc_cpu_do_interrupt
  0,90%  qemu-system-ppc64        [.] object_dynamic_cast_assert
  0,79%  libc-2.13.so             [.] __sigsetjmp
  0,62%  qemu-system-ppc64        [.] type_get_parent.isra.3
  0,58%  qemu-system-ppc64        [.] type_get_by_name
  0,57%  qemu-system-ppc64        [.] qemu_log_mask
  0,54%  qemu-system-ppc64        [.] object_dynamic_cast

qemu-system-sparc64
-------------------
 17,43%  perf-8154.map            [.] 0x7f6ac10245c8                            
                                                                          
 10,46%  qemu-system-sparc64      [.] tcg_optimize                              
                                                                          
 10,36%  qemu-system-sparc64      [.] cpu_sparc_exec                            
                                                                          
  6,35%  qemu-system-sparc64      [.] tb_flush_jmp_cache                        
                                                                          
  4,75%  qemu-system-sparc64      [.] get_physical_address_data                 
                                                                          
  4,45%  qemu-system-sparc64      [.] tcg_liveness_analysis                     
                                                                          
  4,35%  qemu-system-sparc64      [.] tcg_reg_alloc_op                          
                                                                          
  2,90%  qemu-system-sparc64      [.] tlb_flush_page                            
                                                                          
  2,35%  qemu-system-sparc64      [.] disas_sparc_insn                          
                                                                          
  2,28%  qemu-system-sparc64      [.] get_physical_address_code                 
                                                                          
  2,21%  qemu-system-sparc64      [.] tlb_flush                                 
                                                                          
  1,64%  qemu-system-sparc64      [.] tcg_out_opc                               
                                                                          
  1,22%  qemu-system-sparc64      [.] tcg_out_modrm_sib_offset.constprop.41     
                                                                          
  1,20%  qemu-system-sparc64      [.] helper_ld_asi                             
                                                                          
  1,14%  qemu-system-sparc64      [.] gen_intermediate_code_pc                  
                                                                          
  1,04%  qemu-system-sparc64      [.] helper_st_asi                             
                                                                          
  1,00%  qemu-system-sparc64      [.] object_class_dynamic_cast                 
                                                                          
  0,98%  qemu-system-sparc64      [.] tb_find_pc                                
                                                                          
  0,94%  qemu-system-sparc64      [.] get_page_addr_code
  0,92%  qemu-system-sparc64      [.] tcg_gen_code_search_pc
  0,91%  qemu-system-sparc64      [.] tlb_set_page
  0,83%  qemu-system-sparc64      [.] reset_temp
  0,82%  qemu-system-sparc64      [.] tcg_reg_alloc_start


The perf-xxxx.map correspond to the code execution. As you can see it's
a lot lower on sparc, while a lot of smaller code generation/mmu code
appears. It's seems that the optimizations have to be focused on the
system part, not the TCG part, at least for now.

A quick look at the MMU seems to show some performance issue here, due
to the split code/data MMU on SPARC64, while the QEMU TLB is a joint
one. As a consequence one can see a lot of ping pong, setting a given
page to read or read/write, then execution, and later read or read/write
again. My guess is that it's related to constants table in the same page
than the code.

It should also be noted that the tcg_optimize starts to take a
non-negligible time, in both cases. The code grew up quite a lot
recently, and it might be time to rework it. It's nice to have optimized
code, but not if the gain is lower than the optimization time.

I am also surprised to see glib code that high on the qemu-system-ppc64
perf report.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net



reply via email to

[Prev in Thread] Current Thread [Next in Thread]