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Profiling with nSIM NCAM
Yuriy Kolerov edited this page Jul 27, 2023
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1 revision
You can run nSIM in NCAM mode - Near Cycle-Accurate Mode. This mode activates counters that depend on micro-architectural simulations. It may be a good tool for optimization and exploration. NCAM's model is not cycle-accurate and it's not derived from RTL, but it's much faster than xCAM. If you need a cycle-accurate model then consider using xCAM models.
Use -on cycles to enable NCAM:
$ nsimdrv -tcf $NSIM_HOME/etc/tcf/templates/hs38_full.tcf -on cycles main.elf
Use -on nsim_print_stats_on_exit and -on ncam_profiling (this option enables more profiling counters) options to print simulation statistics at the end of a simulation:
$ arc-elf32-gcc -mcpu=archs -specs=hl.specs main.c -o main.elf
$ nsimdrv -tcf $NSIM_HOME/etc/tcf/templates/hs38_full.tcf -on cycles -on ncam_profiling \
-on nsim_print_stats_on_exit main.elf
<Main_Memory>
-------------------------------------------------------------------
Main Memory | Frequency| %
Read | 86| 54.09
Write | 73| 45.91
-------------------------------------------------------------------
Total | 159| 100.00
</Main_Memory>
<L1-I-CACHE>
-------------------------------------------------------------------
L1-I-CACHE | Frequency| %
-------------------------------------------------------------------
Read Hits | 770| 94.48
Read Misses | 45| 5.52
-------------------------------------------------------------------
Total | 815| 100.00
</L1-I-CACHE>
<L1-D-CACHE>
-------------------------------------------------------------------
L1-D-CACHE | Frequency| %
-------------------------------------------------------------------
RW Misses | 17| 4.47
RW Hits | 363| 95.53
Read Hits | 89| 23.42
Read Misses | 1| 0.26
Write Hits | 274| 94.48
Write Misses | 16| 4.21
Dirty Misses | 0| 0.00
-------------------------------------------------------------------
Span Lines | 2| 0.53
Double Miss | 0| 0.00
-------------------------------------------------------------------
Total | 380| 100.00
</L1-D-CACHE>
<Statistics-Branch_Predictor_FB-GShare>
Description: FB-GShare Branch Predictor Statistics
-------------------------------------------------------------------
BPU (Two-Level) | Frequency| %
-------------------------------------------------------------------
Correctly Predicted | 327| 76.05
Miss Predicted | 103| 23.95
Conditional Misses | 26| 25.24
Uconditional Misses | 77| 74.76
-------------------------------------------------------------------
Total | 430| 100.00
</Statistics-Branch_Predictor_FB-GShare>
<Histogram-Instructions>
-------------------------------------------------------------------
Instruction | Frequency| %
-------------------------------------------------------------------
stw | 302| 25.44
nop | 197| 16.60
mov | 128| 10.78
...
neg | 1| 0.08
div | 1| 0.08
-------------------------------------------------------------------
Delay Slot | 55| 4.63
-------------------------------------------------------------------
Total | 1187| 100.00
</Histogram-Instructions>
<Summary-Execution_Profile>
-------------------------------------------------------------------
Execution Profile | Frequency| %
-------------------------------------------------------------------
Interpreted Inst | 1187| 100.00
Cond Branches | 102| 8.59
Cond Branch Mispred | 26| 2.19
Ucond Branches | 121| 10.19
Ucond Branch Mispred | 77| 6.49
-------------------------------------------------------------------
Total | 1187| 100.00
</Summary-Execution_Profile>
<Summary-Simulation_Time>
-------------------------------------------------------------------
Simulation Time | Seconds| %
-------------------------------------------------------------------
Simulation | 0.0032| 99.72
Hostlink | 0.0000| 0.28
-------------------------------------------------------------------
Total | 0.0032| 100.00
</Summary-Simulation_Time>
<Summary-Simulation_Performance>
Instruction Count = 1187 [# Total]
Simulation Time = 0.00 [Seconds]
Simulation Rate = 0.38 [MIPS]
Cycle Count = 2766 [Cycles]
CPI = 2.330
IPC = 0.429
Effective Clock = 0.9 [MHz]
</Summary-Simulation_Performance>
Use -on nsim_trace and -p nsim_trace-output=trace.txt options to trace instructions (omit nsim_trace-output if you want to print trace log right into stdout):
$ nsimdrv -tcf $NSIM_HOME/etc/tcf/templates/hs38_full.tcf -on nsim_trace \
-p nsim_trace-output=trace.txt main.elf
$ head trace.txt
nSIM, Version: 2023.03 (Build: 002)
[0x00000124] 0x226a0280 K lr r2,[0xa] : (w0) r2 <= 0x00000000: aux[0x0a] => 0x00 *
[0x00000128] 0x224f04c2 K bset r2,r2,0x13 : (w0) r2 <= 0x00080000 *
[0x0000012c] 0x20290080 K flag r2 *
[0x00000130] 0x26ab740a 0x00000122 AD K sr 00000122,0x290: aux[0x290] <= 0x122 *
[0x00000138] 0x220a3f80 0x00005c10 AD K mov gp,00005c10 : (w0) r26 <= 0x00005c10 *
[0x00000140] 0x42c3 0x00005b20 AD K mov_s r2,00005b20 : (w0) r2 <= 0x00005b20 *
[0x00000146] 0x26027083 0x00005e34 AD K sub r3,00005e34,r2 : (w0) r3 <= 0x00000314 *