• FizzyOrange
    2·
    2 days ago

    Huge speed-ups for the will-it-scale tlb_flush2_threads test - presumably not very representative!

    I wonder how much effect it has on real world workloads.

  • onlinepersona
    321·
    3 days ago

    More surprising is that it’s taken ~4 years for these Linux kernel patches to materialize with Zen 3 having first debuted in late 2020.

    Reminder: Linux kernel funding is 2% of the Linux foundation’s 200M$/year budget.

    Anti Commercial-AI license

    • grue@lemmy.worldEnglish
      33·
      3 days ago

      the Linux kernel hasn’t widely made use of INVLPGB… In part because Intel engineers typically carry out much of the new x86 instruction optimizations within the Linux kernel and Intel processors do not currently support INVLPGB.

      Sounds like AMD needs to fund more kernel development.

  • SteveTechEnglish
    14·
    3 days ago

    I couldn’t find a hard answer to whether this supports EPYC only, or Ryzen too; so I put together this script to read the CPUID to detect for INVLPGB support according to the AMD64 Programmer’s Manual, and my 7800X3D does not support INVLPGB.

    (Let me know if I’ve made an error though!)

    Code 
    #include <stdio.h>
#include <stdint.h>

int main() {
    uint32_t eax, ebx, ecx, edx;

    eax = 0x80000008;

    __asm__ __volatile__ (
        "cpuid"
        : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
        : "a" (eax)
    );

    printf("EBX: 0x%x\n", ebx);

    if (ebx & (1 << 3)) {
        printf("CPU supports INVLPGB\n");
    } else {
        printf("CPU does not support INVLPGB\n");
    }

    return 0;
}