[External] : Re: Issues with loop unrolling: better pinned node
Rado Smogura
mail at smogura.eu
Fri Aug 27 18:16:58 UTC 2021
Hi all,
I experimented a little bit, and I wonder if this is reasonable, the
outcome on graphs is as expected, and operations looks like properly
ordered (but this is my private opinion).
https://github.com/rsmogura/panama-vector/commit/755b62823aaed0cddf78e8ccfc60c063bb40779a
Kind regards,
Rado
On 19.08.2021 22:26, Rado Smogura wrote:
> I think I answered this question quite simply... it will not work.
>
> On 19.08.2021 18:39, Rado Smogura wrote:
>> Hi all,
>>
>>
>> I hope you have a good day.
>>
>>
>> As still optimizing loops would be good approach, I thought about
>> optimizing a mixed access with this approach:
>>
>>
>> 1. When mixed access is detected set flag "raw / byte array" mixed
>> access.
>>
>> 2. Bail out and restart compilation (will happen during first phases,
>> and only for few methods).
>>
>> 3. Pass a flag to compiler.
>>
>> 4. Modify find_alias_type / flatten_alias_type, so that if byte array
>> will be queried for alias, raw ptr and raw alias will be used.
>>
>>
>> Kind regards,
>>
>> Rado
>>
>> On 18.08.2021 09:17, Rado Smogura wrote:
>>> Hi Vladimir,
>>>
>>>
>>> Thank you for answer.
>>>
>>>
>>> In fact, it is was an attempt to confirm that memory flow can be a
>>> cause why loop opts do not work. That's very fair point. I'll think
>>> about it and maybe I'll be able to come out idea how this can be
>>> generalized.
>>>
>>>
>>> Kind regards,
>>>
>>> Rado
>>>
>>> On 16.08.2021 15:41, Vladimir Ivanov wrote:
>>>>> I wonder what do you think about something like this [1] - it's
>>>>> virtually small single class change
>>>>
>>>> Very interesting experiment, Rado! It's encouraging to hear that
>>>> loop opts immediately benefit from it.
>>>>
>>>> From a architectural perspective, a separate pass to optimize
>>>> memory graph brings excessive complexity:
>>>>
>>>> (1) yet another pass over the graph and susceptible to pass
>>>> ordering issues;
>>>>
>>>> (2) separate from GVN: you either have to duplicate GVN-based
>>>> memory optimizations or run new pass with IGVN in a loop until it
>>>> stabilizes.
>>>>
>>>> IMO the problem you noticed illustrates a general weakness in GVN
>>>> implementation and that's the place where it should be fixed
>>>> (ideally).
>>>>
>>>> Best regards,
>>>> Vladimir Ivanov
>>>>
>>>>>
>>>>> This change tries to find unique memory for load node. I
>>>>> implemented it as separate phase, as optimization may not run in
>>>>> Ideal method. I think it's ligher than phi split out.
>>>>>
>>>>> Loops has been transformed. RCE started.
>>>>>
>>>>> Kind regards,
>>>>> Rado
>>>>>
>>>>> [1] -
>>>>> https://github.com/rsmogura/panama-vector/commit/a44f515890d2c4df3fd0e0ced76545a7664926c3
>>>>> <https://urldefense.com/v3/__https://github.com/rsmogura/panama-vector/commit/a44f515890d2c4df3fd0e0ced76545a7664926c3__;!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvu60z1vk$>
>>>>>
>>>>> [2] -
>>>>> https://github.com/rsmogura/panama-vector/tree/housekeeping-load-memory-optimiziation
>>>>> <https://urldefense.com/v3/__https://github.com/rsmogura/panama-vector/tree/housekeeping-load-memory-optimiziation__;!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvkGUL-Pw$>
>>>>> (full test case)
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>> *From:* Radosław Smogura on behalf of Radosław Smogura
>>>>> <mail at smogura.eu>
>>>>> *Sent:* Friday, August 6, 2021 22:43
>>>>> *To:* Radosław Smogura <mail at smogura.eu>; Paul Sandoz
>>>>> <paul.sandoz at oracle.com>; Vladimir Ivanov
>>>>> <vladimir.x.ivanov at oracle.com>
>>>>> *Cc:* panama-dev at openjdk.java.net <panama-dev at openjdk.java.net>
>>>>> *Subject:* Re: Issues with loop unrolling: better pinned node
>>>>> Hi all,
>>>>>
>>>>> Now when I checked it again. it works as expected, and it's the
>>>>> same code.
>>>>>
>>>>> In draft code I check if the buffer is direct by using type
>>>>> checking to unswitch loop, as unswitching over ByteBuffer.hb did
>>>>> not work (the graph was quite similar). However, I thought that
>>>>> this unswitch actually helped to build correct loops, and any kind
>>>>> of improvement around it would be rather for the purpose of
>>>>> better-looking code.
>>>>>
>>>>> But it looks like that sometimes (but only sometimes) loop still
>>>>> can not be correctly built, or maybe the full optimization kicks
>>>>> in very, very late.
>>>>>
>>>>> Kind regards,
>>>>> Rado
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>> *From:* panama-dev <panama-dev-retn at openjdk.java.net> on behalf of
>>>>> Radosław Smogura <mail at smogura.eu>
>>>>> *Sent:* Friday, August 6, 2021 20:22
>>>>> *To:* Paul Sandoz <paul.sandoz at oracle.com>
>>>>> *Cc:* panama-dev at openjdk.java.net <panama-dev at openjdk.java.net>
>>>>> *Subject:* Re: Issues with loop unrolling: better pinned node
>>>>> Yes,
>>>>>
>>>>> The normal case looks, good. It's all about polluted cases [1]
>>>>>
>>>>> BR,
>>>>> Rado
>>>>>
>>>>> [1] https://github.com/openjdk/panama-vector/pull/109
>>>>> <https://urldefense.com/v3/__https://github.com/openjdk/panama-vector/pull/109__;!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvTXVlXzw$>
>>>>> [https://opengraph.githubassets.com/daf8e3b93dd4c25e04d1ce6ae2a91e1b725625bfd85b5027c61fb78ae3a6a361/openjdk/panama-vector/pull/109]<https://github.com/openjdk/panama-vector/pull/109
>>>>> <https://urldefense.com/v3/__https://opengraph.githubassets.com/daf8e3b93dd4c25e04d1ce6ae2a91e1b725625bfd85b5027c61fb78ae3a6a361/openjdk/panama-vector/pull/109**A3Chttps:/*github.com/openjdk/panama-vector/pull/109__;XSUv!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvjOF75Zk$>>
>>>>>
>>>>> (Draft) Perofrmance improvements for polluted cases by rsmogura ·
>>>>> Pull Request #109 ·
>>>>> openjdk/panama-vector<https://github.com/openjdk/panama-vector/pull/109>
>>>>> <https://urldefense.com/v3/__https://github.com/openjdk/panama-vector/pull/109*3E__;JQ!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvXk316cU$>
>>>>>
>>>>> Hi all, I would like to submit this piece of work, for byte
>>>>> buffers and polluted cases. It resolves some performance issues
>>>>> related to mem barriers when in scope are both on- and off-heap
>>>>> buffer. T...
>>>>> github.com
>>>>>
>>>>> [https://opengraph.githubassets.com/5fde12f89c012a2abef1542ed59c7272429fa7556f6e82a5e617a293d3a5bee1/openjdk/panama-vector]<https://github.com/openjdk/panama-vector/compare/vectorIntrinsics...rsmogura:vectors-polluted-cases?expand=1
>>>>> <https://urldefense.com/v3/__https://opengraph.githubassets.com/5fde12f89c012a2abef1542ed59c7272429fa7556f6e82a5e617a293d3a5bee1/openjdk/panama-vector**A3Chttps:/*github.com/openjdk/panama-vector/compare/vectorIntrinsics...rsmogura:vectors-polluted-cases?expand=1__;XSUv!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvt9bVEEU$>>
>>>>>
>>>>> Comparing
>>>>> openjdk:vectorIntrinsics...rsmogura:vectors-polluted-cases ·
>>>>> openjdk/panama-vector<https://github.com/openjdk/panama-vector/compare/vectorIntrinsics...rsmogura:vectors-polluted-cases?expand=1>
>>>>> <https://urldefense.com/v3/__https://github.com/openjdk/panama-vector/compare/vectorIntrinsics...rsmogura:vectors-polluted-cases?expand=1*3E__;JQ!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvW2CiAB0$>
>>>>>
>>>>> Panama vector. Contribute to openjdk/panama-vector development by
>>>>> creating an account on GitHub.
>>>>> github.com
>>>>>
>>>>> ________________________________
>>>>> From: Paul Sandoz <paul.sandoz at oracle.com>
>>>>> Sent: Friday, August 6, 2021 20:04
>>>>> To: Radosław Smogura <mail at smogura.eu>
>>>>> Cc: panama-dev at openjdk.java.net <panama-dev at openjdk.java.net>
>>>>> Subject: Re: Issues with loop unrolling: better pinned node
>>>>>
>>>>> I am confused as to the case under test. In your initial email of
>>>>> this thread were you also referring implicitly to polluted cases?
>>>>>
>>>>> Paul.
>>>>>
>>>>>> On Aug 6, 2021, at 10:56 AM, Radosław Smogura <mail at smogura.eu>
>>>>>> wrote:
>>>>>>
>>>>>> Hi Paul,
>>>>>>
>>>>>> There's a performance improvement, but. I still can't unroll
>>>>>> polluted cases (I cherry-picked loop unrolling). The graph still
>>>>>> has few nodes taking buffer limit from phi, and on IR I don't see
>>>>>> vectors nodes cascading.
>>>>>>
>>>>>> make test TEST='micro:ByteBufferVectorAccess.p' MICRO="OPTIONS=-f
>>>>>> 1 -prof perfasm
>>>>>> -jvmArgsPrepend=-Djdk.incubator.vector.VECTOR_ACCESS_OOB_CHECK=0"
>>>>>> JOBS=12
>>>>>> Benchmark (size) Mode Cnt
>>>>>> Score Error Units
>>>>>> ByteBufferVectorAccess.pollutedBuffers2 1024 avgt 30
>>>>>> 40.472 ? 1.055 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers2:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers3 1024 avgt 30
>>>>>> 79.251 ? 0.786 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers3:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers4 1024 avgt 30
>>>>>> 83.627 ? 2.140 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers4:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers5 1024 avgt 30
>>>>>> 85.561 ? 1.156 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers5:?asm 1024
>>>>>> avgt NaN
>>>>>>
>>>>>> make test TEST='micro:ByteBufferVectorAccess.p' MICRO="OPTIONS=-f
>>>>>> 1 -prof perfasm"
>>>>>> Benchmark (size) Mode Cnt
>>>>>> Score Error Units
>>>>>> ByteBufferVectorAccess.pollutedBuffers2 1024 avgt 10
>>>>>> 49.326 ? 0.843 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers2:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers3 1024 avgt 10
>>>>>> 100.291 ? 1.271 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers3:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers4 1024 avgt 10
>>>>>> 101.494 ? 1.027 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers4:?asm 1024
>>>>>> avgt NaN ---
>>>>>> ByteBufferVectorAccess.pollutedBuffers5 1024 avgt 10
>>>>>> 94.606 ? 1.522 ns/op
>>>>>> ByteBufferVectorAccess.pollutedBuffers5:?asm 1024
>>>>>> avgt NaN
>>>>>>
>>>>>>
>>>>>> BR,
>>>>>> Rado
>>>>>> From: Paul Sandoz <paul.sandoz at oracle.com>
>>>>>> Sent: Friday, August 6, 2021 18:04
>>>>>> To: Radosław Smogura <mail at smogura.eu>
>>>>>> Cc: panama-dev at openjdk.java.net <panama-dev at openjdk.java.net>
>>>>>> Subject: Re: Issues with loop unrolling: better pinned node
>>>>>>
>>>>>> Hi Rado,
>>>>>>
>>>>>> It’s good you are looking at the IR
>>>>>>
>>>>>> Out of curiosity, what happens if you turn off bounds checking [*]?
>>>>>>
>>>>>> Paul.
>>>>>>
>>>>>> [*]
>>>>>> -Djdk.incubator.vector.VECTOR_ACCESS_OOB_CHECK=0
>>>>>>
>>>>>> > On Aug 6, 2021, at 8:39 AM, Radosław Smogura <mail at smogura.eu>
>>>>>> wrote:
>>>>>> >
>>>>>> > Hi all,
>>>>>> >
>>>>>> > I've found that even if we get rid of barriers, the loop can't
>>>>>> get unrolled, and not needed code is inside it.
>>>>>> >
>>>>>> > I've found this graph, I wonder if it's most optimal, in a
>>>>>> partiucalry Load of ByteBuffer index / hb is from phi, could it
>>>>>> be attached to initial memory?
>>>>>> >
>>>>>> > Here's a picture
>>>>>> https://drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> <https://urldefense.com/v3/__https://drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing__;!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvDYUmUX8$>
>>>>>
>>>>>> >
>>>>>> [https://lh6.googleusercontent.com/SKgGZgfVWFpG8w4mWqguLSU4DVfa1MKYPSQhxv8EoX04XzVz8U8Kc4zHP0iwdR26Suc=w1200-h630-p]<https://drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> <https://urldefense.com/v3/__https://lh6.googleusercontent.com/SKgGZgfVWFpG8w4mWqguLSU4DVfa1MKYPSQhxv8EoX04XzVz8U8Kc4zHP0iwdR26Suc=w1200-h630-p**A3Chttps:/*drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing__;XSUv!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvT2w-EKw$>>
>>>>>
>>>>>> >
>>>>>> bb_issues.png<https://drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> <https://urldefense.com/v3/__https://drive.google.com/file/d/1G7ZN0xHOVIVHmZ_5TTIUdm3F30okAzvO/view?usp=sharing__;!!ACWV5N9M2RV99hQ!c_1aeHKPVlV91PddNfGPUgWISKQSh-fctE1r_hS0mCRD7zdKUeyFHAZBxTadx8tvDYUmUX8$>>
>>>>>
>>>>>> > drive.google.com
>>>>>> >
>>>>>> >
>>>>>> > And sample code
>>>>>> >
>>>>>> > protected void copyMemory(ByteBuffer in, ByteBuffer out) {
>>>>>> > var limit = SPECIES.loopBound(in.limit());
>>>>>> > for (int i=0; i < limit; i += SPECIES.vectorByteSize()) {
>>>>>> > final var v = ByteVector.fromByteBuffer(SPECIES, in, i,
>>>>>> ByteOrder.nativeOrder());
>>>>>> > v.intoByteBuffer(out, i, ByteOrder.nativeOrder());
>>>>>> > }
>>>>>> > }
>>>>>> >
>>>>>> > Kind regards,
>>>>>> > Rado
>>>>>
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