Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 7 Feb 2020 13:11:54 +0100 | Subject | Re: [PATCH -v2 08/10] m68k,mm: Extend table allocator for multiple sizes |
| |
Hoi Peter,
On Fri, Feb 7, 2020 at 12:34 PM Peter Zijlstra <peterz@infradead.org> wrote: > On Fri, Feb 07, 2020 at 11:56:40AM +0100, Geert Uytterhoeven wrote: > > On Fri, Jan 31, 2020 at 1:56 PM Peter Zijlstra <peterz@infradead.org> wrote: > > > In addition to the PGD/PMD table size (128*4) add a PTE table size > > > (64*4) to the table allocator. This completely removes the pte-table > > > overhead compared to the old code, even for dense tables. > > > > Thanks for your patch! > > > > > Notes: > > > > > > - the allocator gained a list_empty() check to deal with there not > > > being any pages at all. > > > > > > - the free mask is extended to cover more than the 8 bits required > > > for the (512 byte) PGD/PMD tables. > > > > Being an mm-illiterate, I don't understand the relation between the number > > of bits and the size (see below). > > If the table translates 7 bits of the address, it will have 1<<7 entries. > > > > - NR_PAGETABLE accounting is restored. > > > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > > > WARNING: Missing Signed-off-by: line by nominal patch author 'Peter > > Zijlstra <peterz@infradead.org>' > > (in all patches) > > > > I can fix that (the From?) up while applying. > > I'm not sure where that warning comes from, but if you feel it needs > fixing, sure. I normally only add the (Intel) thing to the SoB. I've so > far never had complaints about that.
Checkpatch doesn't like this.
> > > --- a/arch/m68k/mm/motorola.c > > > +++ b/arch/m68k/mm/motorola.c > > > @@ -72,24 +72,35 @@ void mmu_page_dtor(void *page) > > > arch/sparc/mm/srmmu.c ... */ > > > > > > typedef struct list_head ptable_desc; > > > -static LIST_HEAD(ptable_list); > > > + > > > +static struct list_head ptable_list[2] = { > > > + LIST_HEAD_INIT(ptable_list[0]), > > > + LIST_HEAD_INIT(ptable_list[1]), > > > +}; > > > > > > #define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru)) > > > #define PD_PAGE(ptable) (list_entry(ptable, struct page, lru)) > > > -#define PD_MARKBITS(dp) (*(unsigned char *)&PD_PAGE(dp)->index) > > > +#define PD_MARKBITS(dp) (*(unsigned int *)&PD_PAGE(dp)->index) > > > + > > > +static const int ptable_shift[2] = { > > > + 7+2, /* PGD, PMD */ > > > + 6+2, /* PTE */ > > > +}; > > > > > > -#define PTABLE_SIZE (PTRS_PER_PMD * sizeof(pmd_t)) > > > +#define ptable_size(type) (1U << ptable_shift[type]) > > > +#define ptable_mask(type) ((1U << (PAGE_SIZE / ptable_size(type))) - 1) > > > > So this is 0xff for PGD and PMD, like before, and 0xffff for PTE. > > Why the latter value? > > The PGD/PMD being 7 bits are sizeof(unsigned long) << 7, or 512 bytes > big. In one 4k page, there fit 8 such entries. 0xFF is 8 bits set, one > for each of the 8 512 byte fragments. > > For the PTE tables, which are 6 bit and of sizeof(unsigned long) << 6, > or 256 bytes, we can fit 16 in one 4k page, resulting in 0xFFFF.
Thanks!
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
| |