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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - OpenMP runtime detects incorrect processor topology on AMD CPUs"
href="https://bugs.llvm.org/show_bug.cgi?id=40727">40727</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>OpenMP runtime detects incorrect processor topology on AMD CPUs
</td>
</tr>
<tr>
<th>Product</th>
<td>OpenMP
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Runtime Library
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>steven@uplinklabs.net
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>The processor topology detection in the OpenMP runtime is confused by AMD CPUs:
$ env KMP_AFFINITY=scatter,verbose ./nbody --bodies 64 --no-crosscheck
--iterations 1 --cycle-after 5
OMP: Info #211: KMP_AFFINITY: decoding x2APIC ids.
OMP: Info #212: KMP_AFFINITY: cpuid leaf 11 not supported - decoding legacy
APIC ids.
OMP: Info #149: KMP_AFFINITY: Affinity capable, using global cpuid info
OMP: Info #154: KMP_AFFINITY: Initial OS proc set respected: 0-15
OMP: Info #156: KMP_AFFINITY: 16 available OS procs
OMP: Info #157: KMP_AFFINITY: Uniform topology
OMP: Info #159: KMP_AFFINITY: 1 packages x 1 cores/pkg x 16 threads/core (1
total cores)
OMP: Info #213: KMP_AFFINITY: OS proc to physical thread map:
OMP: Info #171: KMP_AFFINITY: OS proc 0 maps to package 0 thread 0
OMP: Info #171: KMP_AFFINITY: OS proc 1 maps to package 0 thread 1
OMP: Info #171: KMP_AFFINITY: OS proc 2 maps to package 0 thread 2
OMP: Info #171: KMP_AFFINITY: OS proc 3 maps to package 0 thread 3
OMP: Info #171: KMP_AFFINITY: OS proc 4 maps to package 0 thread 4
OMP: Info #171: KMP_AFFINITY: OS proc 5 maps to package 0 thread 5
OMP: Info #171: KMP_AFFINITY: OS proc 6 maps to package 0 thread 6
OMP: Info #171: KMP_AFFINITY: OS proc 7 maps to package 0 thread 7
OMP: Info #171: KMP_AFFINITY: OS proc 8 maps to package 0 thread 8
OMP: Info #171: KMP_AFFINITY: OS proc 9 maps to package 0 thread 9
OMP: Info #171: KMP_AFFINITY: OS proc 10 maps to package 0 thread 10
OMP: Info #171: KMP_AFFINITY: OS proc 11 maps to package 0 thread 11
OMP: Info #171: KMP_AFFINITY: OS proc 12 maps to package 0 thread 12
OMP: Info #171: KMP_AFFINITY: OS proc 13 maps to package 0 thread 13
OMP: Info #171: KMP_AFFINITY: OS proc 14 maps to package 0 thread 14
OMP: Info #171: KMP_AFFINITY: OS proc 15 maps to package 0 thread 15
OMP: Info #144: KMP_AFFINITY: Threads may migrate across 1 innermost levels of
machine
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7608 thread 0 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7610 thread 1 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7611 thread 2 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7612 thread 3 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7613 thread 4 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7614 thread 5 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7615 thread 6 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7616 thread 7 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7617 thread 8 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7618 thread 9 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7619 thread 10 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7620 thread 11 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7621 thread 12 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7622 thread 13 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7623 thread 14 bound to OS proc set
0-15
OMP: Info #249: KMP_AFFINITY: pid 7608 tid 7624 thread 15 bound to OS proc set
0-15
$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
Address sizes: 43 bits physical, 48 bits virtual
CPU(s): 16
On-line CPU(s) list: 0-15
Thread(s) per core: 2
Core(s) per socket: 8
Socket(s): 1
NUMA node(s): 1
Vendor ID: AuthenticAMD
CPU family: 23
Model: 8
Model name: AMD Ryzen 7 2700X Eight-Core Processor
Stepping: 2
CPU MHz: 4200.705
CPU max MHz: 3700.0000
CPU min MHz: 2200.0000
BogoMIPS: 7384.85
Virtualization: AMD-V
L1d cache: 32K
L1i cache: 64K
L2 cache: 512K
L3 cache: 8192K
NUMA node0 CPU(s): 0-15
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb
rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf
pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx
f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse
3dnowprefetch osvw skinit wdt tce topoext perfctr_core perfctr_nb bpext
perfctr_llc mwaitx cpb hw_pstate sme ssbd sev ibpb vmmcall fsgsbase bmi1 avx2
smep bmi2 rdseed adx smap clflushopt sha_ni xsaveopt xsavec xgetbv1 xsaves
clzero irperf xsaveerptr arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean
flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif
overflow_recov succor smca
It looks like the OpenMP runtime needs to be taught about the AMD-specific
CPUID leaf 0x8000001E. Or as an ugly fallback, learn topology from
/proc/cpuinfo when leaf 0xb is unavailable?</pre>
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