Regression in Utf8ParserTests

[performanceautofiler]

Run Information

Architecture	x64
OS	Windows 10.0.19042
Baseline	721a802c12b524912b6c398313d8eb5e73dec2ef
Compare	dcfe5bfb690fe74d747bba5d6b664769bc9d652c
Diff	Diff

Regressions in System.Buffers.Text.Tests.Utf8ParserTests

Benchmark	Baseline	Test	Test/Base	Test Quality	Edge Detector	Baseline IR	Compare IR	IR Ratio	Baseline ETL	Compare ETL
TryParseInt64 - Duration of single invocation	19.53 ns	25.11 ns	1.29	0.05	False

Test Report

Repro

git clone https://github.com/dotnet/performance.git
py .\performance\scripts\benchmarks_ci.py -f net6.0 --filter 'System.Buffers.Text.Tests.Utf8ParserTests*'

Details

Payloads

Baseline
Compare

Histogram

System.Buffers.Text.Tests.Utf8ParserTests.TryParseInt64(value: 9223372036854775807)

Docs

Profiling workflow for dotnet/runtime repository
Benchmarking workflow for dotnet/runtime repository

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[kunalspathak]

Possibly introduced in #58677

Tagging subscribers to this area: @JulieLeeMSFT
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Issue Details

---

Run Information

Architecture	x64
OS	Windows 10.0.19042
Baseline	721a802c12b524912b6c398313d8eb5e73dec2ef
Compare	dcfe5bfb690fe74d747bba5d6b664769bc9d652c
Diff	Diff

Regressions in System.Buffers.Text.Tests.Utf8ParserTests

Benchmark	Baseline	Test	Test/Base	Test Quality	Edge Detector	Baseline IR	Compare IR	IR Ratio	Baseline ETL	Compare ETL
TryParseInt64 - Duration of single invocation	19.53 ns	25.11 ns	1.29	0.05	False

Test Report

Repro

git clone https://github.com/dotnet/performance.git
py .\performance\scripts\benchmarks_ci.py -f net6.0 --filter 'System.Buffers.Text.Tests.Utf8ParserTests*'

Details

Payloads

Baseline
Compare

Histogram

System.Buffers.Text.Tests.Utf8ParserTests.TryParseInt64(value: 9223372036854775807)

Docs

Profiling workflow for dotnet/runtime repository
Benchmarking workflow for dotnet/runtime repository

Author:	performanceautofiler[bot]
Assignees:	-
Labels:	os-windows, arch-x64, area-CodeGen-coreclr, untriaged
Milestone:	-

[kunalspathak]

It appears to be regression on AMD64, but not on Intel windows and Linux which makes me wonder if this is noise. I profiled the benchmark and found that TryParseInt64D to be expensive. I was suspecting #58677, but this method doesn't have any EH code. There is no assembly difference before vs. after change. There is no other change in 683899d...3fd30b0 that would have impacted this benchmark.

Here is the graph of Intel x64 (windows) and Ubuntu AMD64.

https://pvscmdupload.blob.core.windows.net/reports/allTestHistory%2frefs%2fheads%2fmain_x64_Windows%2010.0.18362%2fSystem.Buffers.Text.Tests.Utf8ParserTests.TryParseInt64(value%3a%209223372036854775807).html

https://pvscmdupload.blob.core.windows.net/reports/allTestHistory%2frefs%2fheads%2fmain_x64_ubuntu%2018.04%2fSystem.Buffers.Text.Tests.Utf8ParserTests.TryParseInt64(value%3a%209223372036854775807).html

Here is the full history graph of this benchmark on windows amd64 and it looks like there are phases of bimodal behavior:

https://pvscmdupload.blob.core.windows.net/reports/allTestHistory/refs/heads/main_x64_Windows%2010.0.19042/amd/System.Buffers.Text.Tests.Utf8ParserTests.TryParseInt64(value%3a%209223372036854775807).html

I did verify if this is another victim of memory randomization, it appears not to be the case.

-------------------- Histogram --------------------
[17.307 ns ; 17.826 ns) | @@@@@@@@@@@@@@@
---------------------------------------------------

I should mention that the hottest loop in the benchmark is long enough to fit in 2 chunks of 32B and we do not align it that may result in some perf instability.

G_M21515_IG08:              ;; offset=005BH
 00007ffd`65684e7b        443BD1               cmp      r10d, ecx
 00007ffd`65684e7e        7376                 jae      SHORT G_M21515_IG11
; ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (jae: 0 ; jcc erratum) 32B boundary ...............................
 00007ffd`65684e80        4963F2               movsxd   rsi, r10d
 00007ffd`65684e83        400FB63430           movzx    rsi, byte  ptr [rax+rsi]
 00007ffd`65684e88        83C6D0               add      esi, -48
 00007ffd`65684e8b        83FE09               cmp      esi, 9
 00007ffd`65684e8e        7766                 ja       SHORT G_M21515_IG11
 00007ffd`65684e90        4F8D1C9B             lea      r11, [r11+4*r11]
 00007ffd`65684e94        4E8D1C5E             lea      r11, [rsi+2*r11]
 00007ffd`65684e98        41FFC2               inc      r10d
 00007ffd`65684e9b        EBDE                 jmp      SHORT G_M21515_IG08
						;; bbWeight=4    PerfScore 33.00
G_M21515_IG09:              ;; offset=007DH
 00007ffd`65684e9d        443BD1               cmp      r10d, ecx
; ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (cmp: 0 ; jcc erratum) 32B boundary ...............................