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8317976: Optimize SIMD sort for AMD Zen 4 #24053

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8317976: Optimize SIMD sort for AMD Zen 4 #24053

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8de2e2c
JDK-8317976: Enable optimized SIMD sort for AMD Zen 4 & Zen 5
rohitarulraj Mar 14, 2025
4201191
create a separate method to check for cpu's supporting avx512 version…
rohitarulraj Mar 17, 2025
b369de6
Refactor 'supports_avx512_simd_sort' code to make it easily readable
rohitarulraj Mar 27, 2025
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2 changes: 1 addition & 1 deletion src/hotspot/cpu/x86/matcher_x86.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -263,7 +263,7 @@

// Is SIMD sort supported for this CPU?
static bool supports_simd_sort(BasicType bt) {
if (VM_Version::supports_avx512dq()) {
if (VM_Version::supports_avx512_simd_sort()) {
return true;
}
else if (VM_Version::supports_avx2() && !is_double_word_type(bt)) {
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6 changes: 3 additions & 3 deletions src/hotspot/cpu/x86/stubGenerator_x86_64.cpp
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Expand Up @@ -4315,7 +4315,7 @@ void StubGenerator::generate_compiler_stubs() {

// Load x86_64_sort library on supported hardware to enable SIMD sort and partition intrinsics

if (VM_Version::is_intel() && (VM_Version::supports_avx512dq() || VM_Version::supports_avx2())) {
if (VM_Version::supports_avx512dq() || VM_Version::supports_avx2()) {
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@vamsi-parasa vamsi-parasa Mar 17, 2025

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Shouldn't you check for VM_Version::supports_avx512_simd_sort() here as well?

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@rohitarulraj rohitarulraj Mar 17, 2025

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The above condition will hold for all AMD processors. Only for Zen4, even though AVX512 is supported, we want to pick AVX2 version of SIMD sort (due to the regression) which is handled by the code below:

snprintf(ebuf_, sizeof(ebuf_), VM_Version::supports_avx512_simd_sort() ? "avx512_sort" : "avx2_sort");

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@vamsi-parasa vamsi-parasa Mar 17, 2025

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Thanks for the clarification!

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@vamsi-parasa vamsi-parasa Mar 17, 2025

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Also, please update the PR description summarizing the main high-level changes in this PR. Will make it easy for others.

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@rohitarulraj rohitarulraj Mar 17, 2025

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Thanks Vamsi, updated the PR description accordingly.

void *libsimdsort = nullptr;
char ebuf_[1024];
char dll_name_simd_sort[JVM_MAXPATHLEN];
Expand All @@ -4326,10 +4326,10 @@ void StubGenerator::generate_compiler_stubs() {
if (libsimdsort != nullptr) {
log_info(library)("Loaded library %s, handle " INTPTR_FORMAT, JNI_LIB_PREFIX "simdsort" JNI_LIB_SUFFIX, p2i(libsimdsort));

snprintf(ebuf_, sizeof(ebuf_), VM_Version::supports_avx512dq() ? "avx512_sort" : "avx2_sort");
snprintf(ebuf_, sizeof(ebuf_), VM_Version::supports_avx512_simd_sort() ? "avx512_sort" : "avx2_sort");
StubRoutines::_array_sort = (address)os::dll_lookup(libsimdsort, ebuf_);

snprintf(ebuf_, sizeof(ebuf_), VM_Version::supports_avx512dq() ? "avx512_partition" : "avx2_partition");
snprintf(ebuf_, sizeof(ebuf_), VM_Version::supports_avx512_simd_sort() ? "avx512_partition" : "avx2_partition");
StubRoutines::_array_partition = (address)os::dll_lookup(libsimdsort, ebuf_);
}
}
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6 changes: 6 additions & 0 deletions src/hotspot/cpu/x86/vm_version_x86.hpp
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Expand Up @@ -432,6 +432,8 @@ class VM_Version : public Abstract_VM_Version {
enum Extended_Family {
// AMD
CPU_FAMILY_AMD_11H = 0x11,
CPU_FAMILY_AMD_17H = 0x17, /* Zen1 & Zen2 */
CPU_FAMILY_AMD_19H = 0x19, /* Zen3 & Zen4 */
// ZX
CPU_FAMILY_ZX_CORE_F6 = 6,
CPU_FAMILY_ZX_CORE_F7 = 7,
Expand Down Expand Up @@ -771,6 +773,10 @@ class VM_Version : public Abstract_VM_Version {
//
static bool cpu_supports_evex() { return (_cpu_features & CPU_AVX512F) != 0; }

static bool supports_avx512_simd_sort() {
// Disable AVX512 version of SIMD Sort on AMD Zen4 Processors
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@vamsi-parasa vamsi-parasa Mar 17, 2025

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Looks like you forgot to remove the comment: // Disable AVX512 version of SIMD Sort on AMD Zen4 Processors

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@rohitarulraj rohitarulraj Mar 17, 2025

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For Zen4, we are disabling AVX512 version of SIMD Sort and using AVX2 version. So the comment is valid.

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@vamsi-parasa vamsi-parasa Mar 17, 2025

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Got it!

return ((is_intel() || (is_amd() && (cpu_family() > CPU_FAMILY_AMD_19H))) && supports_avx512dq()); }
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@iwanowww iwanowww Mar 25, 2025

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It's quite hard to parse. The following looks clearer to me:

if (supports_avx512dq()) {
  // Disable AVX512 version of SIMD Sort on AMD Zen4 Processors.
  if (is_amd() && cpu_family() == CPU_FAMILY_AMD_19H) {
    return false;
  } 
  return true;
}
return false;

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@vamsi-parasa vamsi-parasa Mar 26, 2025

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I second the suggested refactoring. Need to make sure the original is_intel() check is also included appropriately in the logic :)

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@rohitarulraj rohitarulraj Mar 28, 2025

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It's quite hard to parse. The following looks clearer to me:

if (supports_avx512dq()) {
  // Disable AVX512 version of SIMD Sort on AMD Zen4 Processors.
  if (is_amd() && cpu_family() == CPU_FAMILY_AMD_19H) {
    return false;
  } 
  return true;
}
return false;

Done.


// Intel features
static bool is_intel_family_core() { return is_intel() &&
extended_cpu_family() == CPU_FAMILY_INTEL_CORE; }
Expand Down