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8691a62a19
Summary:
This eps param is used for two distinct things:
* initial point clusterization
* checking clusters against the llvm values
What if one wants to only look at highly different clusters, without changing
the clustering itself? In particular, this helps to weed out noisy measurements
(since the clusterization epsilon is still small, so there is a better chance
that noisy measurements from the same opcode will go into different clusters)
By splitting it into two params it is now possible.
This is nearly-free performance-wise:
Old:
```
$ perf stat -r 25 ./bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency-1.yaml -analysis-inconsistencies-output-file=/tmp/clusters-old.html
no exegesis target for x86_64-unknown-linux-gnu, using default
Parsed 10099 benchmark points
Printing sched class consistency analysis results to file '/tmp/clusters-old.html'
...
Performance counter stats for './bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency-1.yaml -analysis-inconsistencies-output-file=/tmp/clusters-old.html' (25 runs):
390.01 msec task-clock # 0.998 CPUs utilized ( +- 0.25% )
12 context-switches # 31.735 M/sec ( +- 27.38% )
0 cpu-migrations # 0.000 K/sec
4745 page-faults # 12183.732 M/sec ( +- 0.54% )
1562711900 cycles # 4012303.327 GHz ( +- 0.24% ) (82.90%)
185567822 stalled-cycles-frontend # 11.87% frontend cycles idle ( +- 0.52% ) (83.30%)
392106234 stalled-cycles-backend # 25.09% backend cycles idle ( +- 1.31% ) (33.79%)
1839236666 instructions # 1.18 insn per cycle
# 0.21 stalled cycles per insn ( +- 0.15% ) (50.37%)
407035764 branches # 1045074878.710 M/sec ( +- 0.12% ) (66.80%)
10896459 branch-misses # 2.68% of all branches ( +- 0.17% ) (83.20%)
0.390629 +- 0.000972 seconds time elapsed ( +- 0.25% )
```
```
$ perf stat -r 9 ./bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency.yml -analysis-inconsistencies-output-file=/tmp/clusters-old.html
no exegesis target for x86_64-unknown-linux-gnu, using default
Parsed 50572 benchmark points
Printing sched class consistency analysis results to file '/tmp/clusters-old.html'
...
Performance counter stats for './bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency.yml -analysis-inconsistencies-output-file=/tmp/clusters-old.html' (9 runs):
6803.36 msec task-clock # 0.999 CPUs utilized ( +- 0.96% )
262 context-switches # 38.546 M/sec ( +- 23.06% )
0 cpu-migrations # 0.065 M/sec ( +- 76.03% )
13287 page-faults # 1953.206 M/sec ( +- 0.32% )
27252537904 cycles # 4006024.257 GHz ( +- 0.95% ) (83.31%)
1496314935 stalled-cycles-frontend # 5.49% frontend cycles idle ( +- 0.97% ) (83.32%)
16128404524 stalled-cycles-backend # 59.18% backend cycles idle ( +- 0.30% ) (33.37%)
17611143370 instructions # 0.65 insn per cycle
# 0.92 stalled cycles per insn ( +- 0.05% ) (50.04%)
3894906599 branches # 572537147.437 M/sec ( +- 0.03% ) (66.69%)
116314514 branch-misses # 2.99% of all branches ( +- 0.20% ) (83.35%)
6.8118 +- 0.0689 seconds time elapsed ( +- 1.01%)
```
New:
```
$ perf stat -r 25 ./bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency-1.yaml -analysis-inconsistencies-output-file=/tmp/clusters-new.html
no exegesis target for x86_64-unknown-linux-gnu, using default
Parsed 10099 benchmark points
Printing sched class consistency analysis results to file '/tmp/clusters-new.html'
...
Performance counter stats for './bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency-1.yaml -analysis-inconsistencies-output-file=/tmp/clusters-new.html' (25 runs):
400.14 msec task-clock # 0.998 CPUs utilized ( +- 0.66% )
12 context-switches # 29.429 M/sec ( +- 25.95% )
0 cpu-migrations # 0.100 M/sec ( +-100.00% )
4714 page-faults # 11796.496 M/sec ( +- 0.55% )
1603131306 cycles # 4011840.105 GHz ( +- 0.66% ) (82.85%)
199538509 stalled-cycles-frontend # 12.45% frontend cycles idle ( +- 2.40% ) (83.10%)
402249109 stalled-cycles-backend # 25.09% backend cycles idle ( +- 1.19% ) (34.05%)
1847783963 instructions # 1.15 insn per cycle
# 0.22 stalled cycles per insn ( +- 0.18% ) (50.64%)
407162722 branches # 1018925730.631 M/sec ( +- 0.12% ) (67.02%)
10932779 branch-misses # 2.69% of all branches ( +- 0.51% ) (83.28%)
0.40077 +- 0.00267 seconds time elapsed ( +- 0.67% )
lebedevri@pini-pini:/build/llvm-build-Clang-release$ perf stat -r 9 ./bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency.yml -analysis-inconsistencies-output-file=/tmp/clusters-new.html
no exegesis target for x86_64-unknown-linux-gnu, using default
Parsed 50572 benchmark points
Printing sched class consistency analysis results to file '/tmp/clusters-new.html'
...
Performance counter stats for './bin/llvm-exegesis -mode=analysis -benchmarks-file=/home/lebedevri/PileDriver-Sched/benchmarks-latency.yml -analysis-inconsistencies-output-file=/tmp/clusters-new.html' (9 runs):
6947.79 msec task-clock # 1.000 CPUs utilized ( +- 0.90% )
217 context-switches # 31.236 M/sec ( +- 36.16% )
1 cpu-migrations # 0.096 M/sec ( +- 50.00% )
13258 page-faults # 1908.389 M/sec ( +- 0.34% )
27830796523 cycles # 4006032.286 GHz ( +- 0.89% ) (83.30%)
1504554006 stalled-cycles-frontend # 5.41% frontend cycles idle ( +- 2.10% ) (83.32%)
16716574843 stalled-cycles-backend # 60.07% backend cycles idle ( +- 0.65% ) (33.38%)
17755545931 instructions # 0.64 insn per cycle
# 0.94 stalled cycles per insn ( +- 0.09% ) (50.04%)
3897255686 branches # 560980426.597 M/sec ( +- 0.06% ) (66.70%)
117045395 branch-misses # 3.00% of all branches ( +- 0.47% ) (83.34%)
6.9507 +- 0.0627 seconds time elapsed ( +- 0.90% )
```
I.e. it's +2.6% slowdown for one whole sweep, or +2% for 5 whole sweeps.
Within noise i'd say.
Should help with [[ https://bugs.llvm.org/show_bug.cgi?id=40787 | PR40787 ]].
Reviewers: courbet, gchatelet
Reviewed By: courbet
Subscribers: tschuett, RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58476
llvm-svn: 354767
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||
|---|---|---|
| .. | ||
| lib | ||
| CMakeLists.txt | ||
| llvm-exegesis.cpp | ||
| LLVMBuild.txt | ||