From: Pasha Tatashin <redacted>
Date: Fri, 12 May 2017 13:24:52 -0400

Right now it is larger, but what I suggested is to add a new optimized
routine just for this case, which would do STBI for 64-bytes but
without membar (do membar at the end of memmap_init_zone() and
deferred_init_memmap()

#define struct_page_clear(page)                                 \
        __asm__ __volatile__(                                   \
        "stxa   %%g0, [%0]%2\n"                                 \
        "stxa   %%xg0, [%0 + %1]%2\n"                           \
        : /* No output */                                       \
        : "r" (page), "r" (0x20), "i"(ASI_BLK_INIT_QUAD_LDD_P))

And insert it into __init_single_page() instead of memset()

The final result is 4.01s/T which is even faster compared to current
4.97s/T

Ok, indeed, that would work.