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SubjectRe: [RFC][PATCH] srcu: Implement call_srcu()
(2012/02/01 20:01), Avi Kivity wrote:
> On 02/01/2012 01:00 PM, Takuya Yoshikawa wrote:

>> How about just doing:
>>
>> take a spin_lock
>> copy the entire (or some portions of) bitmap locally
>> clear the bitmap
>> unlock
>>
>
> That means that vcpus dirtying memory also have to take that lock, and
> spin while the bitmap is being copied. So kvm_vm_ioctl_get_dirty_log()
> will become faster, at the expense of vcpus, which I think is a bad
> tradeoff.

Almost every caller is already holding the mmu_lock.

Isn't it possible to make others hold the lock only for the case of
marking to the bitmap? (I will check myself too.)


>> write protect the dirty pages based on the copied dirty data
>>
>> copy_to_user
>>
>>
>>
>> I can show you some performance numbers, this weekend, if you like.
>
> That'll be great, numbers are better than speculation.
>

Yes, I already have some good numbers to show (and some patches).

Takuya


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