Improve UseAVX setting and add cpu descriptions for zhaoxin processors.

[David Holmes]

Hi Vic,

It has been a long time since we heard from you. :)

I have filed a JBS issue for this update:

https://bugs.openjdk.org/browse/JDK-8367478

Cheers,
David

On 11/09/2025 11:33 pm, Vic Wang(BJ-RD) wrote:
> Hi All
> 
> Here is the patch that improving the UseAVX setting and add cpu descriptions for zhaoxin processors.
> Can you help to review the patch and assign a number for a pull request?
> Thank you!
> 
> 
> Patch in my fork repository:
> https://github.com/Double-Minds-JV/jdk/commit/06498b42ed54021b3ed14a9ccc9adf52e9360c9c
> 
>> diff --git a/src/hotspot/cpu/x86/vm_version_x86.cpp b/src/hotspot/cpu/x86/vm_version_x86.cpp
>> index 094ab370190..4043b29f18c 100644
>> --- a/src/hotspot/cpu/x86/vm_version_x86.cpp
>> +++ b/src/hotspot/cpu/x86/vm_version_x86.cpp
>> @@ -931,9 +931,17 @@ void VM_Version::get_processor_features() {
>>    if (UseSSE < 1)
>>      _features.clear_feature(CPU_SSE);
>>
>> -  //since AVX instructions is slower than SSE in some ZX cpus, force USEAVX=0.
>> -  if (is_zx() && ((cpu_family() == 6) || (cpu_family() == 7))) {
>> -    UseAVX = 0;
>> +  // ZX cpus specific settings
>> +  if (is_zx() && FLAG_IS_DEFAULT(UseAVX)) {
>> +    if (cpu_family() == 7) {
>> +      if (extended_cpu_model() == 0x5B || extended_cpu_model() == 0x6B) {
>> +        UseAVX = 1;
>> +      } else if (extended_cpu_model() == 0x1B || extended_cpu_model() == 0x3B) {
>> +        UseAVX = 0;
>> +      }
>> +    } else if (cpu_family() == 6) {
>> +      UseAVX = 0;
>> +    }
>>    }
>>
>>    // UseSSE is set to the smaller of what hardware supports and what
>> @@ -2592,6 +2600,7 @@ void VM_Version::resolve_cpu_information_details(void) {
>>
>> const char* VM_Version::cpu_family_description(void) {
>>    int cpu_family_id = extended_cpu_family();
>> +  int cpu_model_id = extended_cpu_model();
>>    if (is_amd()) {
>>      if (cpu_family_id < ExtendedFamilyIdLength_AMD) {
>>        return _family_id_amd[cpu_family_id];
>> @@ -2605,6 +2614,22 @@ const char* VM_Version::cpu_family_description(void) {
>>        return _family_id_intel[cpu_family_id];
>>      }
>>    }
>> +  if (is_zx()) {
>> +    if (cpu_family_id == 7) {
>> +      switch (cpu_model_id) {
>> +        case 0x1B:
>> +          return "wudaokou";
>> +        case 0x3B:
>> +          return "lujiazui";
>> +        case 0x5B:
>> +          return "yongfeng";
>> +        case 0x6B:
>> +          return "shijidadao";
>> +      }
>> +    } else if (cpu_family_id == 6) {
>> +      return "zhangjiang";
>> +    }
>> +  }
>>    if (is_hygon()) {
>>      return "Dhyana";
>>    }
>> @@ -2624,6 +2649,9 @@ int VM_Version::cpu_type_description(char* const buf, size_t buf_len) {
>>    } else if (is_amd()) {
>>      cpu_type = "AMD";
>>      x64 = cpu_is_em64t() ? " AMD64" : "";
>> +  } else if (is_zx()) {
>> +    cpu_type = "Zhaoxin";
>> +    x64 = cpu_is_em64t() ? " x86_64" : "";
>>    } else if (is_hygon()) {
>>      cpu_type = "Hygon";
>>      x64 = cpu_is_em64t() ? " AMD64" : "";
>> @@ -3236,6 +3264,12 @@ int VM_Version::allocate_prefetch_distance(bool use_watermark_prefetch) {
>>      } else {
>>        return 128; // Athlon
>>      }
>> +  } else if (is_zx()) {
>> +    if (supports_sse2()) {
>> +      return 256;
>> +    } else {
>> +      return 128;
>> +    }
>>    } else { // Intel
>>      if (supports_sse3() && is_intel_server_family()) {
>>        if (supports_sse4_2() && supports_ht()) { // Nehalem based cpus
> 
> I have run the jtreg tests after applying the patch, the test-summary shows follows:
>> ==============================
>> Test summary
>> ==============================
>>    TEST                                              TOTAL  PASS  FAIL ERROR  SKIP
>>    jtreg:test/hotspot/jtreg:tier1                     3107  2797     0     0   310
>>    jtreg:test/jdk:tier1                               2513  2472     0     0    41
>>    jtreg:test/langtools:tier1                         4668  4656     0     0    12
>>    jtreg:test/jaxp:tier1                                 0     0     0     0     0
>>    jtreg:test/lib-test:tier1                            38    38     0     0     0
>> ==============================
>> TEST SUCCESS
> 
> Best Regards!
> Vic Wang
> 
> 
> 保密声明：
> 本邮件含有保密或专有信息，仅供指定收件人使用。严禁对本邮件或其内容做任何未经授权的查阅、使用、复制或转发。
> CONFIDENTIAL NOTE:
> This email contains confidential or legally privileged information and is for the sole use of its intended recipient. Any unauthorized review, use, copying or forwarding of this email or the content of this email is strictly prohibited.