[Qemu-devel] Re: [PATCH 1/3] qemu-kvm: Wrap phys_ram_dirty with additional inline functions.

[Avi Kivity <avi@redhat.com>]

On 02/08/2010 12:22 PM, OHMURA Kei wrote:
> We think access phys_ram_dirty through inline functions is better
> than directly for encoupseling reason.
>
> We devided the ram in a 64 pages block. Each block has a counter, which is
> stored in phys_ram_dirty_by_word. It shows the number of dirty pages.
> We will find the 64 pages block is dirty or non-dirty using
> phys_ram_dirty_by_word.
>
> Signed-off-by: OHMURA Kei <ohmura.kei@lab.ntt.co.jp>
> ---
>  cpu-all.h  |   74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  cpu-defs.h |    1 +
>  2 files changed, 75 insertions(+), 0 deletions(-)
>
> diff --git a/cpu-all.h b/cpu-all.h
> index 8ed76c7..2251f14 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -168,6 +168,33 @@ typedef union {
>  } CPU_QuadU;
>  #endif
>  
> +static inline unsigned long unroll_flags_to_ul(int flags)
> +{
> +    unsigned long ret = 0, flags_ul = (unsigned long)flags;
> +
> +#if TARGET_LONG_SIZE == 4
> +    ret |= flags_ul <<  0;
> +    ret |= flags_ul <<  8;
> +    ret |= flags_ul << 16;
> +    ret |= flags_ul << 24;
> +#elif TARGET_LONG_SIZE == 8
> +    ret |= flags_ul <<  0;
> +    ret |= flags_ul <<  8;
> +    ret |= flags_ul << 16;
> +    ret |= flags_ul << 24;
> +    ret |= flags_ul << 32;
> +    ret |= flags_ul << 40;
> +    ret |= flags_ul << 48;
> +    ret |= flags_ul << 56;
>   

HOST_LONG_SIZE, not TARGET_LONG_SIZE.

> @@ -890,9 +923,50 @@ static inline int cpu_physical_memory_get_dirty(ram_addr_t addr,
>  
>  static inline void cpu_physical_memory_set_dirty(ram_addr_t addr)
>  {
> +    if (phys_ram_dirty[addr >> TARGET_PAGE_BITS] != 0xff)
> +        ++phys_ram_dirty_by_word[(addr >> TARGET_PAGE_BITS) / 
> +                                 TARGET_LONG_BITS];
> +
>      phys_ram_dirty[addr >> TARGET_PAGE_BITS] = 0xff;
>  }
>   

Why do you need a counter? It may be sufficient to set a single bit.
This reduces the memory overhead and perhaps cache thrashing.

-- 
error compiling committee.c: too many arguments to function