On Wed, Jan 26, 2011 at 7:22 PM, Robert Jennings <rcj@xxxxxxxxxxxxxxxxxx> wrote: > xvmalloc will not currently function with 64K pages. Newly allocated > pages will be inserted at an offset beyond the end of the first-level > index. This tuning is needed to properly size the allocator for 64K > pages. > > The default 3 byte shift results in a second level list size which can not > be indexed using the 64 bits of the flbitmap in the xv_pool structure. > The shift must increase to 4 bytes between second level list entries to > fit the size of the first level bitmap. > > Here are a few statistics for structure sizes on 32- and 64-bit CPUs > with 4KB and 64KB page sizes. > > bits_per_long 32 64 64 > page_size 4,096 4,096 65,535 > xv_align 4 8 8 > fl_delta 3 3 4 > num_free_lists 508 508 4,094 > xv_pool size 4,144b 8,216b 66,040b > per object overhead 32 64 64 > zram struct 0.5GB disk 512KB 1024KB 64KB > > This patch maintains the current tunings for 4K pages, adds an optimal > sizing for 64K pages and adds a safe tuning for any other page sizes. > > Signed-off-by: Robert Jennings <rcj@xxxxxxxxxxxxxxxxxx> > --- > drivers/staging/zram/xvmalloc_int.h | 18 ++++++++++++++++-- > 1 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/zram/xvmalloc_int.h b/drivers/staging/zram/xvmalloc_int.h > index e23ed5c..051a49b 100644 > --- a/drivers/staging/zram/xvmalloc_int.h > +++ b/drivers/staging/zram/xvmalloc_int.h > @@ -19,7 +19,11 @@ > /* User configurable params */ > > /* Must be power of two */ > +#ifdef CONFIG_64BIT > +#define XV_ALIGN_SHIFT 3 > +#else > #define XV_ALIGN_SHIFT 2 > +#endif > #define XV_ALIGN (1 << XV_ALIGN_SHIFT) > #define XV_ALIGN_MASK (XV_ALIGN - 1) > > @@ -27,8 +31,18 @@ > #define XV_MIN_ALLOC_SIZE 32 > #define XV_MAX_ALLOC_SIZE (PAGE_SIZE - XV_ALIGN) > > -/* Free lists are separated by FL_DELTA bytes */ > -#define FL_DELTA_SHIFT 3 > +/* > + * Free lists are separated by FL_DELTA bytes > + * This value is 3 for 4k pages and 4 for 64k pages, for any > + * other page size, a conservative (PAGE_SHIFT - 9) is used. > + */ > +#if PAGE_SHIFT == 12 > +#define FL_DELTA_SHIFT 3 This is handled by the else branch already, no? > +#elif PAGE_SHIFT == 16 > +#define FL_DELTA_SHIFT 4 > +#else > +#define FL_DELTA_SHIFT (PAGE_SHIFT - 9) > +#endif _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
