Re: [v3 0/9] parallelized "struct page" zeroing

[Pasha Tatashin]

On 05/12/2017 12:57 PM, David Miller wrote:
> From: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> Date: Thu, 11 May 2017 16:59:33 -0400
>
> > We should either keep memset() only for deferred struct pages as what
> > I have in my patches.
> >
> > Another option is to add a new function struct_page_clear() which
> > would default to memset() and to something else on platforms that
> > decide to optimize it.
> >
> > On SPARC it would call STBIs, and we would do one membar call after
> > all "struct pages" are initialized.
>
> No membars will be performed for single individual page struct clear,
> the cutoff to use the STBI is larger than that.

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



Pasha