[14/22] exec: only check relevant bitmaps for cleanliness

Most of the time, not all bitmaps have to be marked as dirty;
do not do anything if the interesting ones are already dirty.
Previously, any clean bitmap would have cause all the bitmaps to be
marked dirty.

In fact, unless running TCG most of the time bitmap operations
are not done at all because memory_region_is_logging returns
zero.  In this case, skip cpu_physical_memory_range_includes_clean
as well.

With this patch, cpu_physical_memory_set_dirty_range is called
unconditionally, so there need not be anymore a separate call to
xen_modified_memory.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 exec.c                  | 18 +++++++++---------
 include/exec/ram_addr.h | 19 +++++++++++++------
 2 files changed, 22 insertions(+), 15 deletions(-)

On Thu, 03/26 18:38, Paolo Bonzini wrote:
> Most of the time, not all bitmaps have to be marked as dirty;
> do not do anything if the interesting ones are already dirty.
> Previously, any clean bitmap would have cause all the bitmaps to be
> marked dirty.
> 
> In fact, unless running TCG most of the time bitmap operations
> are not done at all because memory_region_is_logging returns
> zero.  In this case, skip cpu_physical_memory_range_includes_clean
> as well.
> 
> With this patch, cpu_physical_memory_set_dirty_range is called
> unconditionally, so there need not be anymore a separate call to
> xen_modified_memory.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  exec.c                  | 18 +++++++++---------
>  include/exec/ram_addr.h | 19 +++++++++++++------
>  2 files changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 94b7644..83c58ff 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2236,16 +2236,16 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
>  static void invalidate_and_set_dirty(MemoryRegion *mr, hwaddr addr,
>                                       hwaddr length)
>  {
> -    if (cpu_physical_memory_range_includes_clean(addr, length)) {
> -        uint8_t dirty_log_mask = memory_region_is_logging(mr);
> -        if (dirty_log_mask & (1 << DIRTY_MEMORY_CODE)) {
> -            tb_invalidate_phys_range(addr, addr + length, 0);
> -            dirty_log_mask &= ~(1 << DIRTY_MEMORY_CODE);
> -        }
> -        cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
> -    } else {
> -        xen_modified_memory(addr, length);
> +    uint8_t dirty_log_mask = memory_region_is_logging(mr);
> +    if (dirty_log_mask &&
> +        !cpu_physical_memory_range_includes_clean(addr, length, dirty_log_mask)) {
> +        dirty_log_mask = 0;
> +    }
> +    if (dirty_log_mask & (1 << DIRTY_MEMORY_CODE)) {
> +        tb_invalidate_phys_range(addr, addr + length, 0);
> +        dirty_log_mask &= ~(1 << DIRTY_MEMORY_CODE);
>      }
> +    cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
>  }
>  
>  static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 6c3b74e..b408408 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -90,13 +90,20 @@ static inline bool cpu_physical_memory_is_clean(ram_addr_t addr)
>  }
>  
>  static inline bool cpu_physical_memory_range_includes_clean(ram_addr_t start,
> -                                                            ram_addr_t length)
> +                                                            ram_addr_t length,
> +                                                            uint8_t mask)
>  {
> -    bool vga = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
> -    bool code = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_CODE);
> -    bool migration =
> -        cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_MIGRATION);
> -    return vga || code || migration;
> +    bool clean = false;
> +    if (mask & (1 << DIRTY_MEMORY_VGA)) {
> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
> +    }
> +    if (!clean && (mask & (1 << DIRTY_MEMORY_CODE))) {
> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_CODE);
> +    }
> +    if (!clean && (mask & (1 << DIRTY_MEMORY_MIGRATION))) {
> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_MIGRATION);
> +    }
> +    return clean;
>  }

Out of curiosity, is it valid that a mask bit is cleared but the corresponding
dirty bit is set?

>  
>  static inline void cpu_physical_memory_set_dirty_flag(ram_addr_t addr,
> -- 
> 2.3.3
> 
> 
>

On 27/03/2015 07:10, Fam Zheng wrote:
>>  static inline bool cpu_physical_memory_range_includes_clean(ram_addr_t start,
>> -                                                            ram_addr_t length)
>> +                                                            ram_addr_t length,
>> +                                                            uint8_t mask)
>>  {
>> -    bool vga = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
>> -    bool code = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_CODE);
>> -    bool migration =
>> -        cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_MIGRATION);
>> -    return vga || code || migration;
>> +    bool clean = false;
>> +    if (mask & (1 << DIRTY_MEMORY_VGA)) {
>> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_VGA);
>> +    }
>> +    if (!clean && (mask & (1 << DIRTY_MEMORY_CODE))) {
>> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_CODE);
>> +    }
>> +    if (!clean && (mask & (1 << DIRTY_MEMORY_MIGRATION))) {
>> +        clean = cpu_physical_memory_get_clean(start, length, DIRTY_MEMORY_MIGRATION);
>> +    }
>> +    return clean;
>>  }
> 
> Out of curiosity, is it valid that a mask bit is cleared but the corresponding
> dirty bit is set?

Yes, for example if migration is cancelled you'll have some bits set in
the DIRTY_MEMORY_MIGRATION bitmap, but DIRTY_MEMORY_MIGRATION itself
will not be enabled.

Paolo

>>  
>>  static inline void cpu_physical_memory_set_dirty_flag(ram_addr_t addr,
>> -- 
>> 2.3.3
>>
>>
>>