[External] : Re: SuperWord loop optimization lost after method inlining
Vladimir Kozlov
vladimir.kozlov at oracle.com
Tue Feb 16 22:34:55 UTC 2021
Hi Nicolas,
The file you shared has only assembler code. Yes, it shows that when ArrayFloatToArrayFloatVectorBinding::plus() is
inlined into AVector::plus() it is not vectorized.
But I asked for an other file (hotspot_pid<PID>.log) which is generated when you run app with
-XX:+UnlockDiagnosticVMOptions -XX:+LogCompilation flags. It should start with:
<?xml version='1.0' encoding='UTF-8'?>
<hotspot_log version='160 1' process='2302014' time_ms='1613514688748'>
<vm_version>
<name>
Java HotSpot(TM) 64-Bit Server VM
</name>
<release>
11.0.9+7-LTS
</release>
Thanks,
Vladimir K
On 2/15/21 5:19 AM, Nicolas Heutte wrote:
> Hi Vladimir,
>
> I've tried disabling tiered compilation, as you requested. It seems that the inlining was performed slightly
> differently, but the issue remains. As you can see in this excerpt, the main loop isn't properly vectorized:
>
> 0x00000254b0d4bf54: cmp %r11d,%r8d
> 0x00000254b0d4bf57: jae 0x00000254b0d4c19e
> 0x00000254b0d4bf5d: vmovss 0x10(%rcx,%r8,4),%xmm9 ;*faload {reexecute=0 rethrow=0 return_oop=0}
> ; -
> com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 54 (line 41)
> ; - com.qfs.vector.impl.AVector::plus at 17 (line 204)
> ; - com.qfs.agg.impl.SumVectorAggregationBinding::plus at 2 (line 103)
> ; -
> com.qfs.agg.impl.SumVectorAggregationBinding::safeVectorAggregate at 70 (line 66)
> ; - com.qfs.agg.impl.AVectorAggregationBinding::safeAggregate at 27 (line 118)
>
> 0x00000254b0d4bf64: cmp %ebx,%r8d
> 0x00000254b0d4bf67: jae 0x00000254b0d4c1ec
> 0x00000254b0d4bf6d: vaddss 0x10(%rdi,%r8,4),%xmm9,%xmm9
> 0x00000254b0d4bf74: vmovss %xmm9,0x10(%rcx,%r8,4) ;*fastore {reexecute=0 rethrow=0 return_oop=0}
> ; -
> com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 61 (line 41)
> ; - com.qfs.vector.impl.AVector::plus at 17 (line 204)
> ; - com.qfs.agg.impl.SumVectorAggregationBinding::plus at 2 (line 103)
> ; -
> com.qfs.agg.impl.SumVectorAggregationBinding::safeVectorAggregate at 70 (line 66)
> ; - com.qfs.agg.impl.AVectorAggregationBinding::safeAggregate at 27 (line 118)
>
> 0x00000254b0d4bf7b: inc %r8d ;*iinc {reexecute=0 rethrow=0 return_oop=0}
> ; -
> com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 62 (line 40)
> ; - com.qfs.vector.impl.AVector::plus at 17 (line 204)
> ; - com.qfs.agg.impl.SumVectorAggregationBinding::plus at 2 (line 103)
> ; -
> com.qfs.agg.impl.SumVectorAggregationBinding::safeVectorAggregate at 70 (line 66)
> ; - com.qfs.agg.impl.AVectorAggregationBinding::safeAggregate at 27 (line 118)
>
> 0x00000254b0d4bf7e: cmp %r9d,%r8d
> 0x00000254b0d4bf81: jl 0x00000254b0d4bf54 ;*goto {reexecute=0 rethrow=0 return_oop=0}
> ; -
> com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 65 (line 40)
> ; - com.qfs.vector.impl.AVector::plus at 17 (line 204)
> ; - com.qfs.agg.impl.SumVectorAggregationBinding::plus at 2 (line 103)
> ; -
> com.qfs.agg.impl.SumVectorAggregationBinding::safeVectorAggregate at 70 (line 66)
> ; - com.qfs.agg.impl.AVectorAggregationBinding::safeAggregate at 27 (line 118)
>
>
>
> Here is the link to the full log, should you want to take a look at it:
> https://drive.google.com/file/d/1KQU7wI8NjeElFv6RrQmUsUPRMnAefzhb/view?usp=sharing
> <https://urldefense.com/v3/__https://drive.google.com/file/d/1KQU7wI8NjeElFv6RrQmUsUPRMnAefzhb/view?usp=sharing__;!!GqivPVa7Brio!PBuP6MfDNWUOTe23SSXA0V5wn_VHjv2sjI8POWRwp6mr0wVdIzFhNoVZANb4FqCYKwzapw$>
>
> Best regards,
> Nicolas Heutte
>
> On Thu, Feb 11, 2021 at 7:05 PM Vladimir Kozlov <vladimir.kozlov at oracle.com <mailto:vladimir.kozlov at oracle.com>> wrote:
>
> Changing wide mailing list to JIT compiler only.
>
> This deoptimization is normal in Tiered Compilation - it switched from profiling code (level='3') generated by C1
> compiler to new code generated by C2 (level='4') which does loop optimizations.
>
> Thank you for posting inlining information:
>
> @ 17 com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus (69 bytes) inline (hot)
> \-> TypeProfile (14054/14054 counts) = com/qfs/vector/binding/impl/ArrayFloatToArrayFloatVectorBinding
>
> I thought before that may be call site is not hot but it is not the case.
>
> You can do an other experiment to collect log with disabled Tiered Compilation (only C2 is used): -XX:-TieredCompilation
> Also print assembler code (as you did before) for final compilation to see if loop is still not vectorized.
>
> Is it possible to post log file (on GitHub?) for me to look?
>
> Thanks,
> Vladimir K
>
> On 2/11/21 6:28 AM, Nicolas Heutte wrote:
> > Hi Vladimir,
> >
> > Thank you for your help.
> >
> > I'm currently running Java 11.0.9, and I did not use any VM flag of note.
> >
> > I checked the content of the compilation log, and it seems that ArrayFloatToArrayFloatVectorBinding::plus() was
> > deoptimized in order to allow AVector::plus() to be compiled:
> >
> > <writer thread='11576'/>
> > <task_queued compile_id='17280' method='com.qfs.vector.impl.AVector plus (Lcom/qfs/vector/IVector;)V' bytes='23'
> > count='916' iicount='916' level='3' stamp='7394.056' comment='tiered' hot_count='896'/>
> > <writer thread='15784'/>
> > <deoptimized thread='15784' reason='constraint' pc='0x00000296d0785b94' compile_id='17257' compiler='c1' level='3'>
> > <jvms bci='65' method='com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding plus
> > (Lcom/qfs/vector/IVector;Lcom/qfs/vector/IVector;)V' bytes='69' count='909' backedge_count='155602' iicount='910'/>
> > </deoptimized>
> >
> > The last compilation entry for AVector::plus() is:
> >
> > <writer thread='16380'/>
> > <nmethod compile_id='17317' compiler='c2' level='4' entry='0x00000296d6af32c0' size='1960'
> address='0x00000296d6af3110'
> > relocation_offset='376' insts_offset='432' stub_offset='1040' scopes_data_offset='1152' scopes_pcs_offset='1592'
> > dependencies_offset='1880' nul_chk_table_offset='1896' oops_offset='1064' metadata_offset='1072'
> > method='com.qfs.vector.impl.AVector plus (Lcom/qfs/vector/IVector;)V' bytes='23' count='172425' iicount='172425'
> > stamp='7394.199'/>
> > <make_not_entrant thread='16380' compile_id='17280' compiler='c1' level='2' stamp='7394.199'/>
> > @ 1 com.qfs.vector.array.impl.ArrayFloatVector::getBindingId (4 bytes) inline
> (hot)
> > \-> TypeProfile (14552/14552 counts) = com/qfs/vector/array/impl/ArrayFloatVector
> > @ 7 com.qfs.vector.array.impl.ArrayFloatVector::getBindingId (4 bytes) inline
> (hot)
> > \-> TypeProfile (14150/14150 counts) = com/qfs/vector/array/impl/ArrayFloatVector
> > @ 10 com.qfs.vector.binding.impl.VectorBindings::getBinding (9 bytes) inline (hot)
> > @ 5
> com.qfs.vector.binding.impl.VectorBindings$VectorBindingsProvider::getBinding (22
> > bytes) inline (hot)
> > @ 3
> com.qfs.vector.binding.impl.VectorBindings$VectorBindingsProvider::hasBinding
> > (34 bytes) inline (hot)
> > @ 17 com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus (69
> bytes)
> > inline (hot)
> > \-> TypeProfile (14054/14054 counts) =
> > com/qfs/vector/binding/impl/ArrayFloatToArrayFloatVectorBinding
> > @ 12 com.qfs.vector.array.impl.ArrayFloatVector::size (6 bytes) inline (hot)
> > @ 22 com.qfs.vector.impl.AVector::checkIndex (37 bytes) inline (hot)
> > @ 6 com.qfs.vector.array.impl.ArrayFloatVector::size (6 bytes) inline (hot)
> > @ 27 com.qfs.vector.array.impl.ArrayFloatVector::getUnderlying (5 bytes)
> accessor
> > @ 34 com.qfs.vector.array.impl.ArrayFloatVector::getUnderlying (5 bytes)
> accessor
> > <writer thread='15896'/>
> >
> > Unfortunately, I do not have access to a debug VM build, so I cannot run the second test you recommend.
> >
> > Best regards,
> > Nicolas Heutte
> >
> > On Wed, Feb 10, 2021 at 7:36 PM Vladimir Kozlov <vladimir.kozlov at oracle.com <mailto:vladimir.kozlov at oracle.com>
> <mailto:vladimir.kozlov at oracle.com <mailto:vladimir.kozlov at oracle.com>>> wrote:
> >
> > Hi, Nicolas
> >
> > Looks like, when inlined, the loop from ArrayFloatToArrayFloatVectorBinding::plus() was not optimized at all:
> it is not
> > unrolled and has range checks. Such loops are not vectorized (you need unrolling and no checks).
> >
> > What Java version you are running? What HotSpot VM flags you are using when running application?
> >
> > Run application with -XX:+LogCompilation and look on compilation data in hotspot_pid<PID>.log file for caller
> > AVector::plus().
> >
> > VM also has several flags to trace loop optimizations but they are only available in debug VM build. If you
> have access
> > to such build run with -XX:+PrintCompilation -XX:+TraceLoopOpts flags.
> >
> > Thanks,
> > Vladimir K
> >
> > On 2/10/21 9:24 AM, Nicolas Heutte wrote:
> > > Hi all,
> > >
> > > I am encountering a performance issue caused by the interaction between
> > > method inlining and automatic vectorization.
> > >
> > > Our application aggregates arrays intensively using a method named
> > > ArrayFloatToArrayFloatVectorBinding.plus() with the following code:
> > >
> > > for (int i = 0; i < srcLen; ++i) {
> > >
> > > dstArray[i] += srcArray[i];
> > >
> > > }
> > >
> > > When we microbenchmark this method we observe fast performance close to the
> > > practical memory bandwidth and when we print the assembly code we observe
> > > loop unrolling and automatic vectorization with SIMD instructions.
> > >
> > > 0x000001ef4600abf0: vmovdqu 0x10(%r14,%r13,4),%ymm0
> > >
> > > 0x000001ef4600abf7: vaddps 0x10(%rcx,%r13,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600abfe: vmovdqu %ymm0,0x10(%r14,%r13,4)
> > >
> > > 0x000001ef4600ac05: movslq %r13d,%r11
> > >
> > > 0x000001ef4600ac08: vmovdqu 0x30(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac0f: vaddps 0x30(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac16: vmovdqu %ymm0,0x30(%r14,%r11,4)
> > >
> > > 0x000001ef4600ac1d: vmovdqu 0x50(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac24: vaddps 0x50(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac2b: vmovdqu %ymm0,0x50(%r14,%r11,4)
> > >
> > > 0x000001ef4600ac32: vmovdqu 0x70(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac39: vaddps 0x70(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac40: vmovdqu %ymm0,0x70(%r14,%r11,4)
> > >
> > > 0x000001ef4600ac47: vmovdqu 0x90(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac51: vaddps 0x90(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac5b: vmovdqu %ymm0,0x90(%r14,%r11,4)
> > >
> > > 0x000001ef4600ac65: vmovdqu 0xb0(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac6f: vaddps 0xb0(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac79: vmovdqu %ymm0,0xb0(%r14,%r11,4)
> > >
> > > 0x000001ef4600ac83: vmovdqu 0xd0(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600ac8d: vaddps 0xd0(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600ac97: vmovdqu %ymm0,0xd0(%r14,%r11,4)
> > >
> > > 0x000001ef4600aca1: vmovdqu 0xf0(%r14,%r11,4),%ymm0
> > >
> > > 0x000001ef4600acab: vaddps 0xf0(%rcx,%r11,4),%ymm0,%ymm0
> > >
> > > 0x000001ef4600acb5: vmovdqu %ymm0,0xf0(%r14,%r11,4) ;*fastore
> > > {reexecute=0 rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 61
> > > (line 41)
> > >
> > > 0x000001ef4600acbf: add $0x40,%r13d ;*iinc {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 62
> > > (line 40)
> > >
> > > 0x000001ef4600acc3: cmp %eax,%r13d
> > >
> > > 0x000001ef4600acc6: jl 0x000001ef4600abf0 ;*goto {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 65
> > > (line 40)
> > >
> > >
> > >
> > > In the real application, this method is actually inlined in a higher level
> > > method named AVector.plus(). Unfortunately, the inlined version of the
> > > aggregation code is not vectorized anymore:
> > >
> > >
> > >
> > > 0x000001ef460180a0: cmp %ebx,%r11d
> > >
> > > 0x000001ef460180a3: jae 0x000001ef460180e6
> > >
> > > 0x000001ef460180a5: vmovss 0x10(%r8,%r11,4),%xmm1 ;*faload {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 54
> > > (line 41)
> > >
> > > ; -
> > > com.qfs.vector.impl.AVector::plus at 17 (line 204)
> > >
> > > 0x000001ef460180ac: cmp %ecx,%r11d
> > >
> > > 0x000001ef460180af: jae 0x000001ef46018104
> > >
> > > 0x000001ef460180b1: vaddss 0x10(%r9,%r11,4),%xmm1,%xmm1
> > >
> > > 0x000001ef460180b8: vmovss %xmm1,0x10(%r8,%r11,4) ;*fastore {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 61
> > > (line 41)
> > >
> > > ; -
> > > com.qfs.vector.impl.AVector::plus at 17 (line 204)
> > >
> > > 0x000001ef460180bf: inc %r11d ;*iinc {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 62
> > > (line 40)
> > >
> > > ; -
> > > com.qfs.vector.impl.AVector::plus at 17 (line 204)
> > >
> > > 0x000001ef460180c2: cmp %r10d,%r11d
> > >
> > > 0x000001ef460180c5: jl 0x000001ef460180a0 ;*goto {reexecute=0
> > > rethrow=0 return_oop=0}
> > >
> > > ; -
> > > com.qfs.vector.binding.impl.ArrayFloatToArrayFloatVectorBinding::plus at 65
> > > (line 40)
> > >
> > > ; -
> > > com.qfs.vector.impl.AVector::plus at 17 (line 204)
> > >
> > >
> > >
> > > This causes a significant performance drop, compared to a run where we
> > > explicitly disable the inlining and observe automatically vectorized code
> > > again (
> > > -XX:CompileCommand=dontinline,com/qfs/vector/binding/impl/ArrayFloatToArrayFloatVectorBinding.plus
> > > ).
> > >
> > >
> > > How do you guys explain that behavior of the JIT compiler? Is this a known
> > > and tracked issue, could it be fixed in the JVM? Can we do something in the
> > > java code to prevent this from happening?
> > >
> > >
> > > Best regards,
> > >
> > > Nicolas Heutte
> > >
> >
>
More information about the hotspot-compiler-dev
mailing list