Re: [Qemu-devel] vga optmization

["Glauber Costa" <glommer@gmail.com>]

On Tue, Nov 4, 2008 at 9:40 AM, Stefano Stabellini
<stefano.stabellini@eu.citrix.com> wrote:
> andrzej zaborowski wrote:
>
>> Hi,
>>
>> 2008/11/3 Glauber Costa <glommer@redhat.com>:
>> [...]
>>> diff --git a/cpu-all.h b/cpu-all.h
>>> index cdd79bc..9118f4d 100644
>>> --- a/cpu-all.h
>>> +++ b/cpu-all.h
>>> @@ -46,6 +46,8 @@
>>>
>>>  #ifdef BSWAP_NEEDED
>>>
>>> +#include "kvm.h"
>>> +
>>>  static inline uint16_t tswap16(uint16_t s)
>>>  {
>>>     return bswap16(s);
>>> @@ -909,17 +911,10 @@ int cpu_memory_rw_debug(CPUState *env, target_ulong addr,
>>>  #define KQEMU_DIRTY_FLAG     0x04
>>>  #define MIGRATION_DIRTY_FLAG 0x08
>>>
>>> -/* read dirty bit (return 0 or 1) */
>>> -static inline int cpu_physical_memory_is_dirty(ram_addr_t addr)
>>> -{
>>> -    return phys_ram_dirty[addr >> TARGET_PAGE_BITS] == 0xff;
>>> -}
>>> +int cpu_physical_memory_get_dirty(ram_addr_t addr, int dirty_flags);
>>> +int cpu_physical_memory_is_dirty(ram_addr_t addr);
>>>
>>> -static inline int cpu_physical_memory_get_dirty(ram_addr_t addr,
>>> -                                                int dirty_flags)
>>> -{
>>> -    return phys_ram_dirty[addr >> TARGET_PAGE_BITS] & dirty_flags;
>>> -}
>>> +void qemu_physical_sync_dirty_bitmap(ram_addr_t start_addr);
>>
>> This will prevent the functions from being inlined even if KVM is
>> disabled (e.g. on other archs) and I think it could be easily
>> retained.
>>
>
>
> I agree on this.
>
>> void qemu_physical_sync_dirty_bitmap(ram_addr_t start_addr)
>> {
>>     if (kvm_enabled())
>>         kvm_physical_sync_dirty_bitmap(start_addr);
>> }
>>
>
>
> Why don't you make qemu_physical_sync_dirty_bitmap take also and end
> address, and you merge the two bitmaps in this address range in this
> function, so you don't have to change cpu_physical_memory_get_dirty at
> all?
>
> I am saying to do something like:
>
> void qemu_physical_sync_dirty_bitmap(ram_addr_t start_addr, ram_addr_t end_addr)
> {
>        /* sync and merge the two bitmaps between start_addr and end_addr */
> }
>
> then leave cpu_physical_memory_get_dirty untouched.
> I would prefer this approch, it also leaves more space to other
> optimizations.

Either way works for me. I'm fine with your suggestion.
>
>
>



-- 
Glauber  Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."